Apoptosis is induced by sub-acute exposure to 3-MCPD and glycidol on Wistar Albino rat brain cells

3-chloropropane-1,2-diol (3-MCPD) and its toxic metabolite glycidol were classified by the International Agency for Research on Cancer (IARC) as belonging to group 2B and 2A for humans. This study aimed to determine the sub-acute toxicity of these agents. Rats were exposed to 3-MCPD at 0.87 and 10 mg/kg/bw and glycidol (2,4 and 37,5 mg/kg/bw) for 90 days. miR-21 gene expression levels significantly decreased in all group's cerebellar tissues compared with control. Exposure to 10 mg/kg/bw 3-MCPD showed significant increases in PTEN in brain as compared to control group. The Akt gen expressions were significantly decreased in 3-MCPD and glycidol groups when compared to control group brains. Additionally, Caspase 3 and AIF immunopositivity significantly increased in 3-MCPD high dose and glycidol high dose groups in cerebellum granular layers compared to control. The results of the present study conclude that 3-MCPD and glycidol can induce apoptosis in rat brain tissue.

[Toxicological characteristics of the cinnamic]

The toxic properties of the cinnamic alcohol with an aim of its hygienic rating are studied. DL for male rats, male and female mice are respectively 3300, 3000 and 2700 mg/kg. It refers to the substances of hazard class 3. The clinical picture of acute poisoning was characterized by the general depression, muscle relaxation, disorder of the movement coordination, decrease in body temperature and death in the first and the second days after the poisoning. The differences in sex and species sensitivity of the animals to the substance are not observed: the rates of species differences and sex sensitivity are ~1. Single and repeated (10 days) inhalation of the vapors of the cinnamic alcohol at the greatest possible saturation neither cause the death of mice no signs of toxicity. It has a weak ability to cumulation: the cumulation coefficient is 5.4. It has no local irritating action to the skin. Skin-resorptive and sensitizing effects are not revealed. It has a weak irritating effect on the mucous membranes of the eyes. In the subacute experiment after the introduction of the substance into the stomach in a total dose equal to 5.2 DL we noted the lag of the experimental animals in body weight gain from the control ones, the increase in the activity of y-glutamyl transpeptidase and transaminases in serum. In the peripheral blood the decrease in hemoglobin, erythrocytes and eosinophils count is revealed. The threshold of the acute inhalation effect is 140 mg/m (by the reduction in the number of erythrocytes and hemoglobin in peripheral blood). Tentative safe level of the exposure to the cinnamic alcohol in the air of the working zone is 5 mg/m (vapors).

Drosophila melanogaster as a model to characterize fungal volatile organic compounds

Fungi are implicated in poor indoor air quality and may pose a potential risk factor for building/mold related illnesses. Fungi emit numerous volatile organic compounds (VOCs) as alcohols, esters, ethers, ketones, aldehydes, terpenoids, thiols, and their derivatives. The toxicity profile of these VOCs has never been explored in a model organism, which could enable the performance of high throughput toxicological assays and lead to a better understanding of the mechanism of toxicity. We have established a reductionist Drosophila melanogaster model to evaluate the toxicity of fungal VOCs. In this report, we assessed the toxicity of fungal VOCs emitted from living cultures of species in the genera, Trichoderma, Aspergillus, and Penicillium and observed a detrimental effect on larval survival. We then used chemical standards of selected fungal VOCs to assess their toxicity on larval and adult Drosophila. We compared the survival of adult flies exposed to these fungal VOCs with known industrial toxic chemicals (formaldehyde [37%], xylene, benzene, and toluene). Among the tested fungal VOC standards, the compounds with eight carbons (C8) caused greater truncation of fly lifespan than tested non-C8 fungal VOCs and industrial toxins. Our data validate the use of Drosophila melanogaster as a model with the potential to elucidate the mechanistic attributes of different toxic VOCs emitted by fungi and also to explore the potential link between reported human illnesses/symptoms and exposure to water damaged and mold contaminated buildings.

Transient overexpression of adh8a increases allyl alcohol toxicity in zebrafish embryos

Fish embryos are widely used as an alternative model to study toxicity in vertebrates. Due to their complexity, embryos are believed to more resemble an adult organism than in vitro cellular models. However, concerns have been raised with respect to the embryo's metabolic capacity. We recently identified allyl alcohol, an industrial chemical, to be several orders of magnitude less toxic to zebrafish embryo than to adult zebrafish (embryo LC50 = 478 mg/L vs. fish LC50 = 0.28 mg/L). Reports on mammals have indicated that allyl alcohol requires activation by alcohol dehydrogenases (Adh) to form the highly reactive and toxic metabolite acrolein, which shows similar toxicity in zebrafish embryos and adults. To identify if a limited metabolic capacity of embryos indeed can explain the low allyl alcohol sensitivity of zebrafish embryos, we compared the mRNA expression levels of Adh isoenzymes (adh5, adh8a, adh8b and adhfe1) during embryo development to that in adult fish. The greatest difference between embryo and adult fish was found for adh8a and adh8b expression. Therefore, we hypothesized that these genes might be required for allyl alcohol activation. Microinjection of adh8a, but not adh8b mRNA led to a significant increase of allyl alcohol toxicity in embryos similar to levels reported for adults (LC50 = 0.42 mg/L in adh8a mRNA-injected embryos). Furthermore, GC/MS analysis of adh8a-injected embryos indicated a significant decline of internal allyl alcohol concentrations from 0.23-58 ng/embryo to levels below the limit of detection (< 4.6 µg/L). Injection of neither adh8b nor gfp mRNA had an impact on internal allyl alcohol levels supporting that the increased allyl alcohol toxicity was mediated by an increase in its metabolization. These results underline the necessity to critically consider metabolic activation in the zebrafish embryo. As demonstrated here, mRNA injection is one useful approach to study the role of candidate enzymes involved in metabolization.

Toxicity and metabolism of nitroalkanes and substituted nitroalkanes

A series of low molecular weight nitro-containing compounds has recently been discovered to have a variety of biological activities including the reduction of anaerobic methane production in ruminant animals and activity against economically important human pathogens, including Salmonella sp. and shigella-toxin producing Escherichia coli . Although some of these nitrocompounds, nitroethane and 2-nitropropane, for example, have been industrial chemicals and synthetic intermediates for years, others such as carboxymethyl nitro-amino acid analogues are new to science and have not been previously described. The purpose of this paper is to review the toxicological profiles, especially as related to events occurring during metabolism and biotransformation, which contribute to toxicological end points of established nitroaliphatic compounds. It is hoped that by summarizing existing knowledge, an understanding of the activities and toxicological profiles of newly established nitrocompounds might be anticipated or adverse events associated with their use might be avoided.

Moesin is a biomarker for the assessment of genotoxic carcinogens in mouse lymphoma

1,2-Dibromoethane and glycidol are well known genotoxic carcinogens, which have been widely used in industry. To identify a specific biomarker for these carcinogens in cells, the cellular proteome of L5178Y mouse lymphoma cells treated with these compounds was analyzed by 2-dimensional gel electrophoresis (2-DE) and MALDI-TOF mass spectrometry (MS). Of 50 protein spots showing a greater than 1.5-fold increase or decrease in intensity compared to control cells on a 2-D gel, we focused on the candidate biomarker moesin. Western analysis using monoclonal rabbit anti-moesin confirmed the identity of the protein and its increased level of expression upon exposure to the carcinogenic compounds. Moesin expression also increased in cells treated with six additional genotoxic carcinogens, verifying that moesin could serve as a biomarker to monitor phenotypic change upon exposure to genotoxic carcinogens in L5178Y mouse lymphoma cells.

Fragrance material review on 3-phenyl-1-propanol

A toxicologic and dermatologic review of 3-phenyl-1-propanol when used as a fragrance ingredient is presented. 3-Phenyl-1-propanol is a member of the fragrance structural group cinnamyl phenylpropyl compounds. The common characteristic structural element of cinnamyl phenylpropyl materials is an aryl substituted primary alcohol/aldehyde/ester. They are simple aromatic compounds with saturated propyl or unsaturated propenyl side chains containing a primary oxygenated functional group which has little toxic potential. 3-Phenyl-1-propyl derivatives participate in the same beta-oxidation pathways as do their parent cinnamic acid derivatives. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for 3-phenyl-1-propanol was evaluated then summarized and includes physical properties, acute toxicity, skin irritation, skin sensitization, in vitro skin absorption and mutagenicity. A safety assessment of all cinnamyl phenylpropyl compounds will be published simultaneously with this document; please refer to Belsito et al. (2011) for an overall assessment of the safe use of this material and all cinnamyl phenylpropyl materials in fragrances (Belsito, D., Bickers, D., Bruze, M., Dagli, M.L., Fryer, A., Greim, H., Miyachi, Y., Saurat, J.H., Sipes, I.G., 2011. A toxicologic and dermatologic assessment of cinnamyl phenylpropyl compounds when used as fragrance ingredients.).

Toxicology and carcinogenesis studies of propargyl alcohol (CAS No. 107-19-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Propargyl alcohol is a commercially available acetylenic primary alcohol. It is also a by-product in the industrial synthesis of butynediol from acetylene and formaldehyde with copper acetylide as catalyst. Propargyl alcohol is used as a reactant/chemical intermediate, pharmaceutical intermediate, agricultural chemical intermediate, soil fumigant, corrosion inhibitor, solvent stabilizer, and polymer modifier. It has also been used to prevent the hydrogen embrittlement of steel. Propargyl alcohol was nominated by the National Cancer Institute for study because of the potential for human exposure in occupational settings through inhalation and dermal contact. Male and female F344/N rats and B6C3F1 mice were exposed to propargyl alcohol (greater than 99% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90 )(12 minutes) per day, 5 days per week for 16 days. All males exposed to 125 ppm or greater and all females exposed to 250 or 500 ppm died by the end of day 3 of the study, and one 125 ppm female died on day 5. Mean body weights were significantly decreased in 62.5 ppm males and 125 ppm females. Clinical findings in the 125 and 250 ppm groups included lethargy, ataxia, abnormal breathing, and nasal/eye discharge. Right kidney weights of 62.5 and 125 ppm females and liver weights of 125 ppm females were significantly greater than those of the chamber controls. All 250 and 500 ppm males and females had moderate to marked periportal necrosis, congestion, and erythrophagocytosis of the liver. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 17 days. All mice exposed to 125 ppm or greater died by day 3 of the study. Mean body weights of mice exposed to 62.5 ppm were significantly less than those of the chamber controls. Clinical findings in the 62.5 and/or 125 ppm groups included abnormal breathing, nasal/eye discharge, thinness, and lethargy. Right kidney weights of 31.3 ppm mice were significantly greater, and thymus weights of 62.5 ppm males were significantly less than those of the chamber controls. The livers of all males and females exposed to 250 or 500 ppm exhibited marked periportal necrosis, congestion, and erythrophagocytosis; these lesions also occurred in all 125 ppm males with less severity. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. The incidences of minimal to mild hyperplasia of respiratory epithelium of the nose were significantly increased in all exposed groups except 8 ppm males and 4 ppm females. Squamous metaplasia of the respiratory epithelium was noted in a few males and most females exposed to 64 ppm. Necrosis of olfactory epithelium was present in half of the males and females exposed to 64 ppm and in a few males and females exposed to 32 ppm. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 8 ppm or greater and 32 and 64 ppm females were significantly less than those of the chamber control groups. Histopathologic changes occurred in the nasal cavity of mice and involved both the respiratory and olfactory epithelium in groups exposed to 16 ppm or greater. Lesions included minimal to moderate suppurative inflammation, minimal to moderate squamous metaplasia of the respiratory epithelium, minimal to mild hyaline degeneration (accumulation) in the respiratory epithelium, minimal to moderate olfactory epithelial atrophy, minimal to moderate hyperplasia of glands in the olfactory region, minimal necrosis of olfactory epithelium, and minimal to moderate turbinate atrophy. There were no biologically significant differences in organ weights between exposed and chamber control groups. Reproductive tissue parameters of exposed males were similar to those of the chamber controls. Only 2/9 female mice in the 64 ppm group exhibited regular estrous cyclicity compared to 6/10 in the controls. Females exposed to 16 ppm differed from chamber controls in the relative time in the estrous stages, and 64 ppm females had a significantly increased probability of extended estrus. No gross lesions were observed at necropsy. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 16, 32, or 64 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of 32 and 64 ppm males was significantly less than that of the chamber control group. Mean body weights of males exposed to 64 ppm were less than those of the chamber controls after week 24 of the study. Nasal respiratory epithelial adenomas were present in three 64 ppm males and one 32 ppm female; the incidence in 64 ppm males exceeded the historical control ranges. A spectrum of nonneoplastic lesions occurred in the respiratory and olfactory epithelium of rats at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and olfactory basal cell hyperplasia were significantly increased in all exposed groups of rats. The incidences of lesions of the olfactory epithelium including hyperplasia, glandular hyperplasia, atrophy, respiratory metaplasia, degeneration, necrosis, hyaline droplet accumulation, and chronic active inflammation were significantly increased in one or more exposed groups of males and/or females. The incidence of mononuclear cell leukemia was significantly increased in males exposed to 64 ppm, and the incidence exceeded the historical control ranges. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 8, 16, or 32 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups was similar to that of the chamber control groups. Mean body weights of 16 and 32 ppm females were less than those of the chamber control group after weeks 73 and 21, respectively. Eye abnormality (unspecified) was observed after one full year of exposure with the incidence increasing in an exposure concentration-related manner. The incidences of nasal respiratory epithelial adenoma increased with a positive trend and were significantly increased in groups exposed to 32 ppm. A spectrum of nonneoplastic lesions occurred in the nasal respiratory and olfactory epithelium of mice at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and squamous metaplasia were significantly increased in most exposed groups of mice. Suppurative inflammation was often associated with the squamous metaplasia, and turbinate atrophy was present in all exposed mice (except one 16 ppm male). The incidences of olfactory epithelial atrophy and respiratory metaplasia were increased in the 16 and 32 ppm groups. Significantly increased incidences of Harderian gland adenoma occurred in 8 and 32 ppm males.

GENETIC TOXICOLOGY

Propargyl alcohol was mutagenic in Salmonella typhimurium strain TA100 in the absence of liver S9 activation enzymes only; no mutagenicity was observed in TA100 in the presence of S9 enzymes, in TA1535 without S9, or in TA98 with or without S9. In vivo, no significant increases in the frequencies of micronucleated normochromatic erythrocytes were observed in peripheral blood samples from male mice exposed by inhalation to propargyl alcohol for 3 months. In female mice, propargyl alcohol exposure produced a small increase in micronucleated erythrocytes that was judged to be equivocal. No significant changes in the percentage of polychromatic erythrocytes were seen in either male or female mice after 3 months of exposure to propargyl alcohol.

CONCLUSIONS

Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenetic activity of propargyl alcohol in male F344/N rats based on increased incidences of nasal respiratory epithelial adenoma and mononuclear cell leukemia. There was no evidence of carcinogenic activity of propargyl alcohol in female F344/N rats exposed to 16, 32, or 64 ppm. There was some evidence of carcinogenic activity of propargyl alcohol in male and female B6C3F1 mice based on increased incidences of nasal respiratory epithelial adenoma. The increased incidences of Harderian gland adenoma in male B6C3F1 mice may have been related to exposure to propargyl alcohol. Exposure to propargyl alcohol resulted in increased incidences of nonneoplastic nasal lesions in male and female rats and mice. Synonyms: Ethynylcarbinol; 1-hydroxy-2-propyne; 3-hydroxy-1-propyne; PA; 1-propyn-3-ol; 1-propyn-3-yl alcohol; 2-propynol; 3-propynol; propynyl alcohol; 2-propynyl alcohol.

The proposal of architecture for chemical splitting to optimize QSAR models for aquatic toxicity

One of the challenges in the field of quantitative structure-activity relationship (QSAR) analysis is the correct classification of a chemical compound to an appropriate model for the prediction of activity. Thus, in previous studies, compounds have been divided into distinct groups according to their mode of action or chemical class. In the current study, theoretical molecular descriptors were used to divide 568 organic substances into subsets with toxicity measured for the 96-h lethal median concentration for the Fathead minnow (Pimephales promelas). Simple constitutional descriptors such as the number of aliphatic and aromatic rings and a quantum chemical descriptor, maximum bond order of a carbon atom divide compounds into nine subsets. For each subset of compounds the automatic forward selection of descriptors was applied to construct QSAR models. Significant correlations were achieved for each subset of chemicals and all models were validated with the leave-one-out internal validation procedure (R(2)(cv) approximately 0.80). The results encourage to consider this alternative way for the prediction of toxicity using QSAR subset models without direct reference to the mechanism of toxic action or the traditional chemical classification.

Toxicology and carcinogenesis study of glycidol (CAS No. 556-52-5) in genetically modified haploinsufficient p16(Ink4a)/p19(Arf) mice (gavage study)

Glycidol is used as a chemical intermediate in the pharmaceutical industry, as a stabilizer in the manufacture of vinyl polymers, and as an intermediate in the synthesis of glycerol, glycidyl ethers, and amines. Glycidol was nominated for carcinogenicity study by the United States Environmental Protection Agency. Glycidol was selected for study in the haploinsufficient p16(Ink4a)/p19(Arf) mouse because it was found to be carcinogenic in rats and mice in conventional 2-year rodent studies (NTP, 1990), but was negative in a study in p53+/- mice (Tennant et al., 1999). Male and female haploinsufficient p16(Ink4a)/p19(Arf) mice received glycidol (greater than 95% pure) by gavage for 40 weeks. Genetic toxicology studies were conducted in mouse peripheral blood erythrocytes. 40-WEEK STUDY IN MICE: Groups of 15 male and 15 female haploinsufficient p16(Ink4a)/p19(Arf) mice were administered 0, 25, 50, 100, or 200 mg glycidol/kg body weight in deionized water by gavage, 5 days per week for 40 weeks. Survival of 200 mg/kg male and female mice was less than that of the vehicle control groups, but the differences were not significant. Mean body weights of 200 mg/kg male mice and 50, 100, and 200 mg/kg female mice were less than those of the vehicle controls. The left testis, left epididymis, and left cauda epididymis weights were significantly decreased in 200 mg/kg males; the number of sperm heads per cauda epididymis were also significantly decreased in this group. Enlarged spleen and foci of discolored liver were observed in 200 mg/kg male mice at necropsy. These findings corresponded to infiltration by histocytic sarcoma or extramedullary hematopoiesis. The incidences of histiocytic sarcoma were increased in dosed groups of males and in females administered 50 mg/kg or greater, and the incidences in 50 and 200 mg/kg males were significantly greater than that in the vehicle control group. In the lung, incidences of alveolar/bronchiolar adenoma were significantly increased in 100 mg/kg males and 200 mg/kg females; multiple adenomas were seen in some dosed males. Squamous cell papillomas of the forestomach were seen in one 200 mg/kg male, one 100 mg/kg female, and three 200 mg/kg females. Significantly increased incidences of epithelial hyperplasia occurred in the forestomach of 200 mg/kg males and females. Neuronopathy, gliosis, and hemorrhage of the brain were observed at various sites in a few 200 mg/kg males and 100 and/or 200 mg/kg females.

GENETIC TOXICOLOGY

The frequency of micronucleated erythrocytes was monitored in peripheral blood of male and female haploinsufficient p16(Ink4a)/p19(Arf) mice in the 40-week study. No significant increases were observed at 6.5, 13, or 19.5 weeks; small but statistically significant increases were seen in both male and female mice sampled at 26 and 40 weeks.

CONCLUSIONS

Under the conditions of this 40-week gavage study, there was clear evidence of carcinogenic activity of glycidol in male haploinsufficient p16(Ink4a)/p19(Arf) mice based on the occurrence of histiocytic sarcomas. The increased incidences of alveolar/bronchiolar adenomas in male mice were also considered to be related to glycidol administration. There was some evidence of carcinogenic activity of glycidol in haploinsufficient p16(Ink4a)/p19(Arf) female mice based on the occurrence of alveolar/bronchiolar adenoma. The occurrence of forestomach papillomas in female mice may also have been related to glycidol administration. Treatment of male and female haploinsufficient p16(Ink4a)/p19(Arf) mice with glycidol was associated with forestomach hyperplasia and neuronopathy in the and brain.

Neurotoxic Mechanisms of Electrophilic Type-2 Alkenes: Soft Soft Interactions Described by Quantum Mechanical Parameters

Conjugated Type-2 alkenes, such as acrylamide (ACR), are soft electrophiles that produce neurotoxicity by forming adducts with soft nucleophilic sulfhydryl groups on proteins. Soft-soft interactions are governed by frontier molecular orbital characteristics and can be defined by quantum mechanical parameters such as softness (sigma) and chemical potential (mu). The neurotoxic potency of ACR is likely related to the rate of adduct formation, which is reflected in values of sigma. Correspondingly, differences in mu, the ability of a nucleophile to transfer electrons to an electrophile, could determine protein targets of these chemicals. Here, sigma and mu were calculated for a series of structurally similar Type-2 alkenes and their potential sulfhydryl targets. Results show that N-ethylmaleimide, acrolein and methylvinyl ketone were softer electrophiles than methyl acrylate or ACR. Softness (sigma) was closely correlated to corresponding second-order rate constants (k(2)) for electrophile reactions with sulfhydryl groups on N-acetyl-L-cysteine (NAC). The rank order of softness was also directly related to neurotoxic potency as determined by impairment of synaptosomal function and sulfhydryl loss. Calculations of mu showed that the thiolate state of several cysteine analogs was the preferred nucleophilic target of alkene electrophiles. In addition, mu was directly related to the thiolate rate constant (k) for the reaction of the Type-2 alkenes with the cysteine compounds. Finally, in accordance with respective mu values, we found that NAC, but not N-acetyl-L-lysine, protected synaptosomes from toxicity. These findings suggest that the neurotoxicity of ACR and its conjugated alkene analogs is related to electrophilic softness and that the thiolate state of cysteine residues is the corresponding adduct target.

Regeneration of the liver in mice treated with a mixture of hepatotoxins in delayed periods after bone marrow transplantation

Possible effect of bone marrow cells on liver regeneration was studied in mice injected with a mixture of hepatotoxins (allyl alcohol and CCl4) in a dose equal to LD50. The mixture of hepatotoxins was used to minimize the restitution regeneration of the liver. The dose of allyl alcohol causing (in combination with CCl4) maximum liver damage was selected beforehand. Increasing the dose of allyl alcohol in the two-component mixture resulted in more severe necrosis of the liver. The maximum dose of alcohol (50 mg/kg) in combination with CCl4 caused irreversible injury to the liver leading to 100% mortality after 2-4 days. In radiation chimeras reconstituted by bone marrow cell transplantation, in which liver damage was induced by a mixture of hepatotoxins containing the maximum dose of allyl alcohol, we observed normalization of liver tissue structure and function. The mechanism of this effect is not clear.

Fibronectin and laminin induce expression of islet cell markers in hepatic oval cells in culture

Hepatic oval cells (OC) are considered to be facultative liver stem cells and, because they may undergo differentiation into a variety of cell lineages, they might have the potential to be used in cellular therapy. Signals delivered by extracellular matrix (ECM) proteins take part in cellular differentiation in cooperation with signals from growth factors; indeed, some ECM proteins, such as laminin (LAM) and fibronectin (FN), have been shown to contribute to beta-cell differentiation and islet development, respectively. Since no previous studies have investigated the effect of ECM proteins on the expression of islet cell markers by cultured OC, the purpose of the present study was to evaluate whether FN and LAM modulate the expression of genes related to the endocrine pancreas in these liver cells. OC proliferation was induced in Wistar rats by prolonged treatment with 2-acetoaminofluorene/allyl alcohol and confirmed by reverse transcription/polymerase chain reaction and hepatic immunocytochemical and histopathological analyses. OC isolation was performed by Ficoll gradient and magnetic-activated cell sorting. OC were cultured for 1 and 2 months under several conditions with specific growth factors, over a FN or LAM substrate or in high glucose, nicotinamide and fetal calf serum. OC cultured on FN substrate expressed Pdx-1, Pax-6, insulin 2 and glucagon. LAM also induced the expression of Pdx-1, insulin 1 and insulin 2, glucagon, somatostatin and GLUT-2. Our results suggest that these ECM proteins can be used in protocols of OC transdifferentiation aimed at reducing the period necessary for complete transdifferentiation.

Structure-Toxicity Analysis of Type-2 Alkenes: In Vitro Neurotoxicity

Acrylamide (ACR) is a conjugated type-2 alkene that produces synaptic toxicity presumably by sulfhydryl adduction. The alpha,beta-unsaturated carbonyl of ACR is a soft electrophile and, therefore, adduction of nucleophilic thiol groups could occur through a conjugate (Michael) addition reaction. To address the mechanism of thiol adduct formation and corresponding neurotoxicological importance, we defined structure-toxicity relationships among a series of conjugated type-2 alkenes (1 microM-10mM), which included acrolein and methylvinyl ketone. Results show that exposure of rat striatal synaptosomes to these chemicals produced parallel, concentration-dependent neurotoxic effects that were correlated to loss of free sulfhydryl groups. Although differences in relative potency were evident, all conjugated analogs tested were equiefficacious with respect to maximal neurotoxicity achieved. In contrast, nonconjugated alkene or aldehyde congeners did not cause synaptosomal dysfunction or sulfhydryl loss. Acrolein and other alpha,beta-unsaturated carbonyls are bifunctional (electrophilic reactivity at the C-1 and C-3 positions) and could produce in vitro neurotoxicity by forming protein cross-links rather than thiol monoadducts. Immunoblot analysis detected slower migrating, presumably derivatized, synaptosomal proteins only at very high acrolein concentrations (>or= 25 mM). Exposure of synaptosomes to high concentrations of ACR (1M), N-ethylmaleimide (10mM), and methyl vinyl ketone (MVK) (100mM) did not alter the gel migration of synaptosomal proteins. Furthermore, hydralazine (1mM), which blocks the formation of protein cross-links, did not affect in vitro acrolein neurotoxicity. Thus, type-2-conjugated alkenes produced synaptosomal toxicity that was linked to a loss of thiol content. This is consistent with our hypothesis that the mechanism of ACR neurotoxicity involves formation of Michael adducts with protein sulfhydryl groups.

Evaluation of the genotoxic potential of 3-monochloropropane-1,2-diol (3-MCPD) and its metabolites, glycidol and beta-chlorolactic acid, using the single cell gel/comet assay

3-monochloropropane-1,2-diol (3-MCPD) is a member of a group of chemicals known as chloropropanols. It is found in many foods and food ingredients as a result of food processing. 3-MCPD is regarded as a rat carcinogen known to induce Leydig-cell and mammary gland tumours in males and kidney tumours in both genders. The aim of our study was to clarify the possible involvement of genotoxic mechanisms in 3-MCPD induced carcinogenicity at the target organ level. For that purpose, we evaluated DNA damages in selected target (kidneys and testes) and non-target (blood leukocytes, liver and bone marrow) male rat organs by the in vivo alkaline single cell gel electrophoresis (comet) assay, 3 and 24 h after 3-MCPD oral administration to Sprague-Dawley and Fisher 344 adult rats. 3-MCPD may be metabolised to a genotoxic intermediate, glycidol, whereas the predominant urinary metabolite in rats following 3-MCPD administration is beta-chlorolactic acid. Therefore, we also studied the DNA damaging effects of 3-MCPD and its metabolites, glycidol and beta-chlorolactic acid, in the in vitro comet assay on CHO cells. Our results show the absence of genotoxic potential of 3-MCPD in vivo in the target as well as in the non-target organs. Glycidol, the epoxide metabolite, induced DNA damages in CHO cells. beta-Chlorolactic acid, the main metabolite of 3-MCPD in rats, was shown to be devoid of DNA-damaging effects in vitro in mammalian cells.

NTP Technical Report on the comparative toxicity studies of allyl acetate (CAS No. 591-87-7), allyl alcohol (CAS No. 107-18-6) and acrolein (CAS No. 107-02-8) administered by gavage to F344/N rats and B6C3F1 mice

Allyl acetate, allyl alcohol, and acrolein are used in the manufacture of detergents, plastics, pharmaceuticals, and chemicals and as agricultural agents and food additives. Male and female F344/N rats and B6C3F(1) mice received allyl acetate, allyl alcohol, or acrolein by gavage for 14 weeks. Genetic toxicology studies were conducted in Salmonella typhimurium, Drosophila melanogaster, cultured Chinese hamster ovary cells, rat bone marrow erythrocytes, and mouse peripheral blood erythrocytes. Groups of 10 male and 10 female rats were administered 0, 6, 12, 25, 50, or 100 mg allyl acetate/kg body weight, 0, 1.5, 3, 6, 12, or 25 mg/kg allyl alcohol, or 0, 0.75, 1.25, 2.5, 5, or 10 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. Groups of 10 male and 10 female mice were administered 0, 8, 16, 32, 62.5, or 125 mg/kg allyl acetate, 0, 3, 6, 12, 25, or 50 mg/kg allyl alcohol, or 0, 1.25, 2.5, 5, 10, or 20 mg/kg acrolein in 0.5% methylcellulose by gavage, 5 days per week for 14 weeks. In the allyl acetate rat study, all males and females in the 100 mg/kg groups died or were killed moribund by day 8; there were no other deaths. In the allyl alcohol study, all rats survived to the end of the study except one 6 mg/kg female. In the acrolein rat study, eight males and eight females in the 10 mg/kg groups died by week 9 of the study. Two males in the 2.5 and 5 mg/kg groups and one or two females in the 1.25, 2.5, and 5 mg/kg groups also died early; two of these deaths were gavage accidents. In the allyl acetate mouse study, all males and females in the 125 mg/kg group died during the first week of the study. All other early deaths, except five 62.5 mg/kg males and one 32 mg/kg female, were gavage accidents. In the allyl alcohol mouse study, one 50 mg/kg female died due to a gavage accident; all other animals survived to the end of the study. In the acrolein mouse study, all males and females administered 20 mg/kg died during the first week of the study. All other early deaths, except one male and one female administered 10 mg/kg, were unrelated to chemical administration. The concentration of 3-hydroxypropyl mercapturic acid (3-HPM) in the urine of rats and mice was determined after the first dose of chemical and at the end of the 14-week study. At both time points, the concentrations of 3-HPM in the urine of animals that received allyl acetate or allyl alcohol increased linearly with dose. In animals dosed with acrolein, the concentrations of 3-HPM exhibited a nonlinear increase with dose at the first time point. At the end of the study, the concentration of 3-HPM in the urine of animals dosed with acrolein was linear with dose except at the highest concentration administered. Since urine volumes were not recorded during the urine collection, complete quantitation of these data was not possible. The final mean body weights and mean body weight gains of male rats administered 12 or 50 mg/kg allyl acetate and of male and female rats administered 10 mg/kg acrolein were significantly less than those of the vehicle controls. The mean body weight gain of male mice in the 50 mg/kg group in the allyl alcohol study was also less than that of the vehicle controls. Final mean body weights and mean body weight gains of dosed female rats and male and female mice in the allyl acetate studies, male and female rats and female mice in the allyl alcohol studies, and male and female mice in the acrolein studies were generally similar to those of the respective vehicle controls. Clinical findings related to allyl acetate administration included pallor, eye or nasal discharge, ruffled fur, lethargy, diarrhea, and thinness among rats in the 100 mg/kg groups and lethargy, abnormal breathing, thinness, and ruffled fur among mice that died early. In the acrolein study, clinical findings included abnormal breathing, eye or nasal discharge, ruffled fur, thinness, and lethargy in rats in the 10 mg/kg groups. The liver weights of male rats administered 25 mg/kg allyl alcohol, female rats administered 50 mg/kg allyl acetate or 5 or 10 mg/kg acrolein, and male mice administered 10 mg/kg acrolein were significantly greater than those of the vehicle controls. Female rats administered 10 mg/kg acrolein had significantly lower absolute and relative thymus weights than did the vehicle controls. Female rats administered 25 mg/kg allyl alcohol spent more time in diestrus and less time in metestrus than the vehicle controls. The estrous cycles of female mice dosed with 16 or 32 mg/kg allyl acetate were significantly longer than that of the vehicle controls. Gross lesions related to allyl acetate treatment were observed in the liver, forestomach, and thorax/abdomen of male and female rats in the 100 mg/kg groups. Microscopically, the incidences of forestomach squamous epithelial hyperplasia were significantly increased in male rats administered 12 mg/kg or greater, female rats administered 25 or 50 mg/kg, male mice administered 32 or 62.5 mg/kg, and female mice administered 16, 32, or 62.5 mg/kg. Forestomach necrosis, hemorrhage, and inflammation were present in most rats in the 100 mg/kg groups, and the incidence of hemorrhage in 125 mg/kg male mice was increased; male mice in the 62.5 and 125 mg/kg groups and 125 mg/kg female mice had significantly increased incidences of glandular stomach hemorrhage. Increased incidences of several liver lesions occurred in male or female rats administered 50 or 100 mg/kg, and to a lesser extent in 25 mg/kg rats, 62.5 mg/kg male mice, and 125 mg/kg male and female mice. Bone marrow hyperplasia, hemorrhage or depletion in the mediastinal, mandibular, and mesenteric lymph nodes, hemorrhage and necrosis of the thymus, and hematopoietic cell proliferation of the red pulp were also observed in 100 mg/kg rats. Increased incidences of necrosis in the mandibular and mesenteric lymph nodes, spleen, and thymus were observed in 62.5 and 125 mg/kg mice. Male and female rats administered 6 mg/kg allyl alcohol or greater and male and female mice administered 12 mg/kg allyl alcohol or greater had significantly increased incidences of squamous hyperplasia of the forestomach epithelium. Female rats in the 25 mg/kg group had significantly increased incidences of bile duct hyperplasia and periportal hepatocyte hypertrophy in the liver. Incidences of portal cytoplasmic vacuolization were significantly increased in 50 mg/kg male mice and female mice in the 25 and 50 mg/kg groups. Gross lesions related to acrolein treatment were observed in the forestomach and glandular stomach of male and female rats in the 10 mg/kg groups and 20 mg/kg female mice. Microscopically, the incidences of squamous hyperplasia of the forestomach epithelium were significantly increased in male rats in the 5 and 10 mg/kg groups, female rats administered 2.5 mg/kg or greater, and male and female mice administered 2.5, 5, or 10 mg/kg. Male and female rats in the 10 mg/kg groups and 20 mg/kg male and female mice had significantly increased incidences of glandular stomach hemorrhage. Female mice in the 20 mg/kg group also had significantly increased incidences of glandular stomach inflammation and epithelial necrosis. Allyl acetate was mutagenic in S. typhimurium strains TA100 and TA1535, in the absence of S9 activation. With S9, no mutagenicity was detected in these two strains; negative results were obtained in strains TA97 and TA98, with and without S9. Allyl alcohol was not mutagenic in four strains of S. typhimurium, with or without S9 metabolic activation. Acrolein, tested in a preincubation protocol, was weakly mutagenic in S. typhimurium strain TA100 in the presence of 10% induced rat liver S9. Equivocal results were obtained in strains TA100 and TA1535 with 10% induced hamster liver S9. Negative results were obtained with TA97, TA98, and TA1538 under all test conditions, and acrolein gave negative results in all four S. typhimurium strains tested for mutation induction under a vapor protocol. No induction of micronuclei was noted in bone marrow erythrocytes of male rats administered allyl acetate by gavage three times at 24-hour intervals. No significant increases in micronucleated erythrocytes were noted in bone marrow samples from male rats administered allyl alcohol by intraperitoneal injection for 3 days. A small, but significant increase in the frequency of micronucleated normochromatic erythrocytes was observed in the peripheral blood of female mice administered allyl acetate by gavage for 14 weeks; no increase was observed in male mice. No increases in the frequencies of micronucleated normochromatic erythrocytes were observed in the peripheral blood of male or female mice administered allyl alcohol or acrolein by gavage for 14 weeks. Acrolein induced sister chromatid exchanges in cultured Chinese hamster ovary cells in the absence, but not the presence, of S9; it did not induce chromosomal aberrations, with or without S9. Results of three independent Drosophila melanogaster sex linked recessive lethal tests in which acrolein was administered to adult flies via feeding or injection and to larvae via feeding were negative.

The effects of vehicles on the human dermal irritation potentials of allyl esters

Allyl esters, frequently used in the fragrance industry, often contain a certain percentage of free allyl alcohol. Allyl alcohol is known to have a potential for delayed skin irritation. Also present in the finished product are different solvent systems, or vehicles, which are used to deliver the fragrances based upon their intended application. This study was conducted to determine whether different vehicles affect the skin irritation potential of five different allyl esters. The allyl esters tested were allyl amyl glycolate, allyl caproate, allyl (cyclohexyloxy)acetate, allyl cyclohexylpropionate, and allyl phenoxyacetate in the vehicles diethyl phthalate, 3:1 diethyl phthalate:ethanol, and 1:3 diethyl phthalate:ethanol at concentrations of 0.1%, 0.5%, 1.0%, and 2.0% (w/w). A modified cumulative irritation test was conducted in 129 human subjects. Test materials (0.3 ml) were applied under occlusion to skin sites on the back for 1 day (24 h) using Hill Top chambers. Irritation was assessed at 1, 2, 4, and 5 days following application of test materials. Cumulative irritation scores varied considerably among test materials. There were no delayed irritation observations. The highest irritation scores were observed at the 2.0% concentration for all test materials. The irritation scores for allyl amyl glycolate, allyl (cyclohexyloxy)acetate, and allyl phenoxyacetate were highest in 1:3 diethyl phthalate:ethanol, thus the resulting calculated no-observed-effect levels, 0.12%, 0.03%, and 0%, respectively, were much lower for this vehicle compared to the diethyl phthalate vehicle, 0.33%, 0.26%, 0.25%, respectively. These data showed a trend for lower concentration thresholds to induce irritation when higher levels of ethanol were used in the vehicle.

Modeling inflammation-drug interactions in vitro: a rat Kupffer cell-hepatocyte coculture system

Xenobiotic-inflammation interactions lead to hepatotoxicity in vivo. Selected xenobiotic agents (acetaminophen, APAP; chlorpromazine, CPZ; allyl alcohol, AlOH; monocrotaline, MCT) for which this occurs were evaluated for ability to elicit the release of Kupffer cell (KC)-derived inflammatory mediators and to modulate lipopolysaccharide (LPS)-stimulated release of these mediators. Using KCs and hepatocytes (HPCs) isolated from rat, KC/HPC cocultures were treated with either LPS, xenobiotic, vehicle or a combination. Six hours later, the release of inflammatory mediators was assessed. LPS alone caused a concentration-dependent increase in TNF-alpha release but had no significant effect on the release of PGE(2). APAP by itself did not alter release of TNF-alpha, PGE(2), IL-10, Gro/KC or IFN-gamma; however, in the presence of LPS, APAP enhanced LPS-induced TNF-alpha and Gro/KC release. APAP also attenuated LPS-induced increases in IL-10 and MCP-1. CPZ alone caused a concentration-dependent increase in TNF-alpha release, which was approximately additive in the presence of LPS. AlOH alone did not affect TNF-alpha release, but decreased TNF-alpha production in the presence of LPS. AlOH increased PGE(2) production, and this effect was potentiated in the presence of LPS. MCT by itself did not affect release of TNF-alpha but increased the response to LPS. Neither MCT, LPS, nor the combination affected production of PGE(2). These results demonstrate that KC/HPC cocultures can be used to evaluate interactions of xenobiotics with LPS. Furthermore, data from these studies qualitatively mirror reported data from whole animal studies, suggesting that this model could be useful for predicting aspects of xenobiotic-inflammation interactions in vivo.

Protective effect of Phyllanthus fraternus against allyl alcohol-induced oxidative stress in liver mitochondria

The effect of administration of allyl alcohol on the oxidative stress and the protective effect due to administration of an aqueous extract of Phyllanthus fraternus against allyl alcohol-induced damage in liver mitochondria were studied. When rats were treated with allyl alcohol, the rate of mitochondrial respiration was decreased significantly with both NAD(+)- and FAD-linked substrates. The respiratory control ratio, an index of membrane integrity and the P/O ratio, a measure of phosphorylation efficiency also decreased significantly. There was a significant increase in the lipid peroxide level and the protein carbonyl content. A significant decrease was observed in the total sulphydryl groups and a significant increase in the generation of superoxide radicals. Administration of rats with an aqueous extract of Phyllanthus fraternus (100 mg/kg) prior to allyl alcohol administration showed protection of 72, 40 and 80% using glutamate+malate (NADH oxidation) and 77, 54 and 20% using succinate as substrate on state 3, RCR and P/O ratio, respectively. The protection on lipid peroxide level was 88 and 91% in homogenate and mitochondria, respectively. In case of protein carbonyls, total sulphydryl groups and on the generation of superoxide radicals the protection was 99, 59 and 53%, respectively.

Improvement of mortality rate and decrease in histologic hepatic injury after human cord blood stem cell infusion in a murine model of hepatotoxicity

BACKGROUND AND AIMS

Because of their plasticity potential local and systemic application of cord blood stem cells may represent excellent candidates for cell-based therapeutic strategies in toxic liver injuries. It is already known that intraperitoneal administration of hematopoietic stem cells provides rapid liver homing in animal models of hepatic injury. We sought to assess the efficacy of a hematopoietic stem cell infusion to decrease the histologic damage and the mortality rate of animals previously damaged by allyl alcohol.

MATERIAL AND METHODS

NOD/SCID mice were divided into two groups. (1) animals treated by intraperitoneal administration of allyl alcohol and (2) animals treated with allyl alcohol and 24 hours later with an intraperitoneal infusion of human cord blood cells. Flow cytometry, histology, immunohistochemistry, and RT-PCR were performed to monitor human cell engraftment by evidences of human hepatic markers.

RESULTS

Human stem cells were able to transdifferentiate into hepatocytes, improve liver regeneration after damage, and reduce the mortality rate even when requiring qualitative and quantitative differences in the transdifferentiation processes. The mortality rate decreased from 70% to 20%, with a significant improvement in the histologic findings.

CONCLUSION

We demonstrated that the infusion of hematopoietic stem cells into the liver in the early stage of damage might initiate endogenous hepatic tissue regeneration that oppose the injury inflicted by toxicants.

Acute, subchronic, and mutagenicity studies with norbornene fluoroalcohol

The object of this study was to evaluate the toxicity of norbornene fluoroalcohol (NBFOH), which is used as an intermediate in the production of fluorinated monomers and polymers. NBFOH was evaluated for acute oral, dermal, and inhalation toxicity, dermal sensitization using the Local Lymph Node Assay (LLNA), mutagenesis by the Ames assay, and subchronic toxicity in a 4-week inhalation rat study. NBFOH demonstrated slight acute toxicity in oral, dermal, and inhalation studies. Approximate lethal doses of 3400 and > 5000 mg/kg for the oral and dermal routes, respectively, and an approximate lethal concentration of 4300 mg/m(3) were determined. NBFOH demonstrated moderate skin irritation, was a severe eye irritant, produced dermal sensitization, but did not cause bacterial mutagenicity either in the presence or absence of S9 activation. Male and female rats were exposed nose only to airborne NBFOH at levels of 0, 410, 1400, and 1500 mg/m(3), 6 h/day, 5 days/week for 4 weeks with clinical and histopathology specimens collected 1 day after the final exposure. Due to the vapor pressure of NBFOH, the 1500 mg/m(3) atmosphere was 27% aerosol and 73% vapor; the 1400 mg/m(3) atmosphere was 5% aerosol and 95% vapor, and the 410 mg/m(3) level was only vapor. No test substance-related mortality or clinical signs of toxicity were observed over the course of the study, and male rats demonstrated significant weight loss and decreased food consumption at 1400 mg/m(3). Male rats from the 1500 mg/m(3) group demonstrated an 11% increase in prothrombin time that was significantly higher than the control value. Examination of fluoride in the urine did not demonstrate a concentration-response relationship, with minimal elevations observed in male rats at all exposure levels and sporadic increases in females. Both male and female rats exposed to 1400 mg/m(3) or greater had squamous metaplasia of the laryngeal mucosa and degeneration of the nasal olfactory and respiratory mucosa. Based on the above findings, NBFOH demonstrates the potential to produce allergic contact dermatitis, and subchronic inhalation studies indicate a no-observed-adverse-effect-level (NOAEL) of 410 mg/m(3).

Comparison of murine cirrhosis models induced by hepatotoxin administration and common bile duct ligation

AIM: To build up the research models of hepatic fibrosis in mice.

METHODS: Inbred wild-type FVB/N mice were either treated with alpha-naphthyl-isothiocyanate (ANIT), allyl alcohol (AA), carbon tetrachloride (CCl₄), 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), and silica, or subjected to common bile duct ligation (CBDL) to induce hepatic injury. Liver biopsies were performed every 4 wk to evaluate hepatic fibrosis over a period of 6 mo. Cumulative cirrhosis and survival curves were constructed by life table method and compared with Wilcoxon test.

RESULTS: Under the dosages used, there was neither mortality nor cirrhosis in AA and silica-treated groups. DDC and ANIT caused cirrhosis within 4-12 and 12-24 wk, respectively. Both showed significantly faster cirrhosis induction at high dosages without significant alteration of survival. The duration for cirrhosis induction by CCl₄ ranged from 4 to 20 wk, mainly dependent upon the dosage. However, the increase in CCl₄ dosage significantly worsened survival. Intraperitoneal CCl₄ administration resulted in better survival in comparison with gavage administration at high dosage, but not at medium and low dosages. After CBDL, all the mice developed liver cirrhosis within 4-8 wk and then died by the end of 16 wk.

CONCLUSION: CBDL and administrations of ANIT, CCl₄, and DDC ensured liver cirrhosis. CBDL required the least amount of time in cirrhosis induction, but caused shortened lives of mice. It was followed by DDC and ANIT administration with favorable survival. As for CCl₄, the speed of cirrhosis induction and the mouse survival depended upon the dosages and the administration route.

Human Cordonal Stem Cell Intraperitoneal Injection Can Represent a Rescue Therapy After an Acute Hepatic Damage in Immunocompetent Rats

BACKGROUND AND AIM

Tissue homeostasis and turnover require reserve stem proliferating cells. Several studies performed on immunodeficient animals have suggested a degree of plasticity by the hematopoietic stem cell compartment that may represent source for liver regeneration. We sought to explore the hepatic differentiation potential of hematopoietic stem cells from human cord blood, after toxic liver damage induced by allyl-alcohol in immunocompetent rats.

MATERIALS AND METHODS

Wistar rats were divided into groups (A) allyl-alcohol intraperitoneal injection with hematopoietic stem cell intraperitoneal infusion at 1 day and sacrifice 3 days later; (B) stem cell injection and sacrifice 3 days later; (C) allyl-alcohol infusion and sacrifice 4 days later; and (D) sacrifice without any treatment. Livers, spleens, and bone marrows were analysed for human stem cells using flow-cytometry; livers were also tested by histology and immunohistochemistry to study the pattern of hepatic regeneration after damage and human stem cell conversion into hepatocyte-like cells, respectively.

RESULTS

Flow-cytometry revealed selective recruitment of human hematopoietic stem cells by damaged livers (group A) compared with control group B. In addition, liver damage was reduced in animals treated with stem cells. Immunohistochemistry demonstrated that human stem cells could convert hepatic cells.

CONCLUSIONS

Our study demonstrated that hematopoietic stem cells selectively recruited by injured livers can contribute to hepatic regeneration after acute toxic damage in immunocompetent recipients.

Dose-dependent liver regeneration in chloroform, trichloroethylene and allyl alcohol ternary mixture hepatotoxicity in rats

The present study was designed to examine the hypothesis that liver tissue repair induced after exposure to chloroform (CF) + trichloroethylene (TCE) + allyl alcohol (AA) ternary mixture (TM) is dose-dependent similar to that elicited by exposure to these compounds individually. Male Sprague Dawley (S-D) rats (250-300 g) were administered with fivefold dose range of CF (74-370 mg/kg, ip), and TCE (250-1250 mg/kg, ip) in corn oil and sevenfold dose range of AA (5-35 mg/kg, ip) in distilled water. Liver injury was assessed by plasma alanine amino transferase (ALT) activity and liver tissue repair was measured by (3) H-thymidine incorporation into hepatonuclear DNA. Blood and liver levels of parent compounds and two major metabolites of TCE [trichloroacetic acid (TCA) and trichloroethanol (TCOH)] were quantified by gas chromatography. Blood and liver CF and AA levels after TM were similar to CF alone or AA alone, respectively. However, the TCE levels in blood and liver were substantially decreased after TM in a dose-dependent fashion compared to TCE alone. Decreased plasma and liver TCE levels were consistent with decreased production of metabolites and elevated urinary excretion of TCE. The antagonistic interaction resulted in lower liver injury than the summation of injury caused by the individual components at all three-dose levels. On the other hand, tissue repair showed a dose-response leading to regression of injury. Although the liver injury was lower and progression was contained by timely tissue repair, 50% mortality occurred only with the high dose combination, which is several fold higher than environmental levels. The mortality could be due to the central nervous system toxicity. These findings suggest that exposure to TM results in lower initial liver injury owing to higher elimination of TCE, and the compensatory liver tissue repair stimulated in a dose-dependent manner mitigates progression of injury after exposure to TM.

Toxicity and metabolism of the conjugates of 3-nitropropanol and 3-nitropropionic acid in forages poisonous to livestock

Glycosides of 3-nitro-1-propanol (nitropropanol) and glucose esters of 3-nitro-1-propanoic acid (nitropropionic acid) occur in many forages distributed throughout the world. Systemically, nitropropionic acid irreversibly inactivates succinate dehydrogenase, thereby blocking ATP formation. Nitropropanol is not toxic per se in mammals but is converted to nitropropionic acid by hepatic alcohol dehydrogenase. Nitrotoxins can be metabolized by rumen microbes, which may provide a mechanism for detoxification. At least 20 different ruminal bacteria are known to metabolize the nitrotoxins, but most appear to play a minor role in detoxification. Evidence suggests that an obligate anaerobic nitro-respiring bacterium, Denitrobacterium detoxificans, may be particularly important in conferring protection to animals consuming the nitrotoxins as this bacterium metabolizes the toxins at rates near those by mixed ruminal populations. Rates of ruminal nitrotoxin metabolism can be enhanced by modifying the rumen environment through dietary manipulations, which suggests in vivo enrichment of competent nitrotoxin-metabolizing bacteria such as D. detoxificans.

Protein binding and metabolism influence the relative skin sensitization potential of cinnamic compounds

Skin protein modification (haptenation) is thought to be a key step in the manifestation of sensitization to low molecular mass chemicals (<500 g/mol). For sensitizing chemicals that are not protein reactive, it is hypothesised that metabolic activation can convert such chemicals into protein reactive toxins within the skin. trans-Cinnamaldehyde, alpha-amyl cinnamaldehyde, and trans-cinnamic alcohol are known sensitizers with differing potencies in man, where the former two are protein reactive and the latter is not. Here, we have used immunochemical methods to investigate the extent of protein-cinnamaldehyde binding in rat and human skin homogenates that have been incubated (for either 5, 15, 30, or 60 min) at 37 degrees C with cinnamaldehyde, alpha-amyl cinnamaldehyde (at concentrations of between 1 and 40 mM), and cinnamic alcohol (at higher concentrations of 200 or 400 mM). Cinnamaldehyde specific antiserum was raised specially. A broad range (in terms of molecular mass) of protein-cinnamaldehyde adducts was detected (as formed in a time- and concentration-dependent manner) in skin treated with cinnamaldehyde and cinnamic alcohol but not with alpha-amyl cinnamaldehyde. Mechanistic observations have been related to relative skin sensitization potential, as determined using the local lymph node assay (LLNA) as a biological read-out. The work presented here suggests that there is a common hapten involved in cinnamaldehyde and cinnamic alcohol sensitization and that metabolic activation (to cinnamaldehyde) is involved in the latter. Conversely, there does not appear to be a common hapten for cinnamaldehyde and alpha-amyl cinnamaldehyde. Such mechanistic work on protein modification is important in understanding the early mechanisms of skin sensitization. Such knowledge can then be used in order that effective and appropriate in vitro/in silico tools for predicting sensitization potential, with a high confidence, can be developed.

A human umbilical cord stem cell rescue therapy in a murine model of toxic liver injury

BACKGROUND

Several studies have demonstrated that bone marrow contains a subpopulation of stem cells capable of participating in the hepatic regenerative process, even if some reports indicate quite a low level of liver repopulation by human stem cells in the normal and transiently injured liver.

AIMS

In order to overcome the low engraftment levels seen in previous models, we tried the direct intraperitoneal administration of human cord blood stem cells, using a model of hepatic damage induced by allyl alcohol in NOD/SCID mice.

METHODS

We designed a protocol based on stem cell infusion following liver damage in the absence of irradiation. Flow cytometry, histology, immunohistochemistry and RT-PCR for human hepatic markers were performed to monitor human cell engraftment.

RESULTS

Human stem cells were able to transdifferentiate into hepatocytes, to improve liver regeneration after damage and to reduce the mortality rate both in both protocols, even if with qualitative and quantitative differences in the transdifferentiation process.

CONCLUSIONS

We demonstrated for the first time that the intraperitoneal administration of stem cells can guarantee a rapid liver engraftment. Moreover, the new protocol based on stem cell infusion following liver damage in the absence of irradiation may represent a step forward for the clinical application of stem cell transplantation.

Neutrophils contribute to endotoxin enhancement of allyl alcohol hepatotoxicity

Nontoxic doses of endotoxin (lipopolysaccharide, LPS) enhance the hepatotoxicity of many xenobiotic agents, including allyl alcohol. Systemic LPS exposure induces an inflammatory response, including accumulation and activation of neutrophils (PMNs) in the liver. The hypothesis that PMNs play a causal role in LPS enhancement of allyl alcohol hepatotoxicity was tested. Rats were pretreated with an anti-neutrophil antibody (anti-PMN immunoglobulin [lg]) to deplete circulating PMNs. Subsequently, they were given LPS or its vehicle, and 2 h later allyl alcohol was administered. The numbers of circulating and hepatic PMNs were decreased in rats pretreated with anti-PMN lg, and liver toxicity induced by cotreatment with LPS and allyl alcohol was attenuated. Treatment with allyl alcohol diminishes the concentration of reduced glutathione (GSH) in liver, raising the possibility that antioxidant defense was compromised in these livers. Accordingly, the hypothesis was tested that allyl alcohol-induced reduction in GSH renders liver cells more sensitive to reactive oxygen species produced by activated PMNs. Isolated hepatocytes were incubated with allyl alcohol in the presence and absence of isolated PMNs stimulated to produce reactive oxygen species. Allyl alcohol produced a concentration-dependent increase in ALT release from hepatocytes. Activated PMNs produced a statistically significant increase in cell killing that was so small it is unlikely to explain the role of PMNs in liver injury in vivo. To test the hypothesis that proteases released from activated PMNs increase the sensitivity of liver cells to allyl alcohol, isolated hepatocytes were incubated with medium from PMNs activated to undergo degranulation. Protease-containing medium from PMNs did not affect allyl alcohol-induced release of ALT from hepatocytes. Taken together, these results indicate that PMNs play a role in the potentiation of allyl alcohol toxicity by LPS. It is unlikely that PMNs contribute to this injury through release of reactive oxygen species or proteases, and other mechanisms must be involved.

Strong protein adduct trapping accompanies abolition of acrolein-mediated hepatotoxicity by hydralazine in mice

Acrolein is a highly reactive alpha,beta-unsaturated aldehyde that readily alkylates nucleophilic centers in cell macromolecules. Typically, such reactions proceed via Michael addition chemistry, forming adducts that retain an electrophilic carbonyl group. Since these species participate in secondary deleterious reactions, we hypothesize that inactivation of carbonyl adducts may attenuate acrolein toxicity. Indeed, we recently established that the nucleophilic antihypertensive drug hydralazine readily "traps" acrolein adducts in cell proteins and strongly suppresses acrolein-mediated toxicity in isolated hepatocytes. This work sought to determine whether hydralazine prevents the in vivo hepatotoxicity of the acrolein precursor allyl alcohol in whole mice and whether adduct trapping accompanies any such hepatoprotection. Mice received allyl alcohol alone or in conjunction with several doses of hydralazine. Four hours later, mice were sacrificed to allow for the determination of liver enzymes in plasma as markers of hepatic injury, whereas livers were assessed for glutathione and hydralazine-stabilized protein adducts. Hydralazine afforded strong, dose-dependent protection against the increases in plasma marker enzymes but not the hepatic glutathione depletion produced by allyl alcohol. Western blotting revealed intense, dose-dependent adduct trapping by hydralazine in numerous liver proteins over a broad 26- to 200-kDA mass range. In keeping with these findings, immunohistochemical analysis of liver slices indicated diffuse, extranuclear adduct trapping by hydralazine that was uniformly distributed across the liver lobule, with partial localization in parenchymal cell membranes. These findings concur with our hypothesis that hydralazine readily inactivates reactive carbonyl-retaining protein adducts formed by acrolein, thereby preventing secondary reactions that trigger cellular death.

Histological and lipid peroxidation changes after administration of 2-acetylaminofluorene in a rat liver injury model following selective periportal and pericentral damage

Administration of 2-acetylaminofluorene (2-AAF) suppresses mature hepatocyte proliferation following selective periportal or pericentral damage induced by allyl-alcohol (AA) or carbon tetrachloride (CCl(4)) administration, respectively. The aim of the present study was to investigate the histological and the lipid peroxidation changes after 2-AAF administration following CCl(4) and AA treatment. The study comprised 108 male Wistar rats that were assigned in four groups: Group A: a placebo pellet was implanted in their neck and on 7th day single dosages of AA and CCl(4) were administrated. Group B: 28-day release 2-AAF pellets (7 0mg-2.5mg per day) were implanted on the neck and on 7th day received a single dose of CCl(4). Group C: 28-day release 2-AAF pellets (70-2.5mg per day) were implanted on the neck and on 7th day a single dose of AA and CCl(4) were administrated. Group D: Sham-operated. Rats of each group were sacrificed on the 9th, 11th, 13th and 21st day. Liver tissue was obtained for histological examination and blood was collected for lipid peroxidation evaluation by measuring malondialdehyde (MDA) and for liver enzymes. On the 9th and 21st day the histological score of liver necrosis was statistically higher on Groups B and C compared to Group A. Concentration of MDA in Group A was significantly higher than in Groups B and C on 9th and 11th days. Transaminase levels, however, were significantly higher in Group A on 9th day compare to the Groups B and C. In conclusion, it appears that oxidative stress was correlated with liver necrosis and with liver regeneration. Suppression of liver regeneration after 2-AAF administration leads to lower malondialdehyde concentrations.

The FEMA GRAS assessment of cinnamyl derivatives used as flavor ingredients

This publication is the seventh in a series of safety evaluations performed by the Expert Panel of the Flavor and Extract Manufacturers Association (FEMA). In 1993, the Panel initiated a comprehensive program to re-evaluate the safety of more than 1700 GRAS flavoring substances under conditions of intended use. Elements that are fundamental to the safety evaluation of flavor ingredients include exposure, structural analogy, metabolism, pharmacokinetics and toxicology. Flavor ingredients are evaluated individually and in the context of the available scientific information on the group of structurally related substances. Scientific data relevant to the safety evaluation of the use of cinnamyl derivatives as flavoring ingredients is evaluated.

15-Deoxy Prostaglandin J2 Enhances Allyl Alcohol-Induced Toxicity in Rat Hepatocytes

Allyl alcohol causes hepatotoxicity that is potentiated by small doses of bacterial lipopolysaccharide (LPS) through a cyclooxygenase-2 (COX-2)-dependent mechanism. The COX-2 product prostaglandin D(2) (PGD(2)) increases hepatocyte killing by allyl alcohol in vitro. In the present study the ability of the nonenzymatic product of PGD(2), 15-deoxy-Delta12,14-prostaglandin J(2) (15d-PGJ(2)), to increase the cytotoxicity of allyl alcohol was evaluated. In a concentration-dependent manner, 15d-PGJ(2) significantly augmented cell death caused by allyl alcohol in isolated rat hepatocytes. 15d-PGJ(2) also increased the cytotoxicity of acrolein, the active metabolite of allyl alcohol. An agonist for the PGD(2) receptor neither reproduced the increase in allyl alcohol-mediated cytotoxicity nor altered the response to 15d-PGJ(2). Similarly, these responses were not affected by either an agonist or an antagonist for the peroxisome proliferator-activated receptor-gamma. The enhancement by 15d-PGJ(2) of allyl alcohol-mediated cell killing was unaffected by augmentation or inhibition of cAMP. Protein synthesis was markedly decreased by 15d-PGJ(2), but inhibition of protein synthesis alone with cycloheximide did not increase allyl alcohol-mediated cell killing. Allyl alcohol at subtoxic concentrations increased translocation of nuclear factor kappa B (NF-kappaB), whereas at cytotoxic concentrations no translocation occurred. 15d-PGJ(2) inhibited translocation of NF-kappaB from the cytosol to the nucleus both in the presence and absence of allyl alcohol. Like 15d-PGJ(2), MG132, an inhibitor of NF-kappaB activation, enhanced allyl alcohol-induced hepatocyte death. Together these results indicate that 15d-PGJ(2) augments hepatocyte killing by allyl alcohol, and the mechanism may be related to the inhibition of NF-kappaB activation.

Tissue repair plays pivotal role in final outcome of liver injury following chloroform and allyl alcohol binary mixture

The objective of this study was to evaluate the interaction profile of chloroform (CHCl(3))+allyl alcohol (AA) binary mixture (BM)-induced acute hepatotoxic response. Plasma alanine aminotransferase (ALT) was measured to assess liver injury, and 3H-thymidine (3H-T) incorporation into hepatonuclear DNA was measured as an index of liver regeneration over a time course of 0-72 h. Male Sprague-Dawley (S-D) rats received single ip injection of 5-fold dose range of CHCl(3) (74, 185 and 370 mg/kg) in corn oil (maximum 0.5 ml/kg) and 7-fold dose range of AA (5, 20 and 35 mg/kg) in distilled water simultaneously. The doses for BM were selected from individual toxicity studies of CHCl(3) alone [Int. J. Toxicol. 22 (2003) 25], and AA alone [Reg. Pharmacol. Toxicol. 19 (1999) 165]. Since the highest dose of each treatment (CHCl(3)- 740 and AA- 50 mg/kg) yielded mortality due to the suppressed tissue repair followed by liver failure, this dose was omitted for BM. The levels of CHCl(3) (30-360 min) and AA (5-60 min) were quantified in blood and liver by gas chromatography (GC). The liver injury was more than additive after BM compared to CHCl(3) alone or AA alone at highest dose combination (370+35 mg/kg), which peaked at 24 h. The augmented liver injury observed with BM was consistent with the quantitation data. Though the liver injury was higher, the greater stimulation of tissue repair kept injury from progressing, and rescued the rats from hepatic failure and death. At lower dose combinations, the liver injury was no more than additive. Results of the present study suggest that liver tissue repair, in which liver tissue lost to injury is promptly replaced, plays a pivotal role in the final outcome of liver injury after exposure to BM of CHCl(3) and AA.

Allyl alcohol activation of protein kinase C delta leads to cytotoxicity of rat hepatocytes

Hepatotoxicity of allyl alcohol involves its bioactivation to acrolein and subsequent protein sulfhydryl loss and lipid peroxidation. However, the links between these events and hepatocellular death are not known. The purpose of these studies was to examine whether specific signal transduction pathways are associated with allyl alcohol toxicity in hepatocytes. Inhibition or augmentation of cyclic AMP and/or protein kinase A (PKA) by Rp-Ado-3N,5N-cyclic monophosphorothioate triethylamine salt or 3-isobutyl-1-methylxanthine had no effect on allyl alcohol-induced cell death. H-7, an inhibitor of PKA, PKC, and PKG, partially inhibited cell killing by allyl alcohol, whereas chelerythrine chloride, a nonselective PKC inhibitor, almost completely abolished allyl alcohol cytotoxicity. Neither 2,2N,3,3N,4,4N-hexahydroxy-1,1N,-biphenyl-6,6N-dimethanol-dimethyl ether, a selective PKC alpha and beta inhibitor, nor bisindolylmaleimide I, an inhibitor of PKC alpha, beta, and epsilon, had any effect on allyl alcohol cytotoxicity. In contrast, rottlerin, a selective PKCdelta inhibitor, blocked hepatocellular killing by allyl alcohol. Cytoprotection by chelerythrine chloride and rottlerin was not the result of inhibition of bioactivation of allyl alcohol because each inhibitor also prevented cell death from acrolein. Western blotting and immunohistochemical techniques revealed that allyl alcohol stimulated phosphorylation and translocation of PKCdelta to hepatocyte membranes (i.e., activation), and this activity was inhibited by rottlerin. Cell death appeared to occur via oncotic necrosis rather than apoptosis based on single-stranded DNA ELISA and propidium iodide staining. Together, these results indicate that activation of PKCdelta is a critical, early event in initiating hepatocyte injury and death from allyl alcohol.

Primary cultures of human hepatocytes as a tool in cytotoxicity studies: cell protection against model toxins by flavonolignans obtained from Silybum marianum

The aim of this study was to evaluate the cytoprotective effects upon primary human hepatocytes of silymarin extract and its main flavonolignans following exposure to the cytotoxic actions of model toxins. The conditions for the hepatocyte intoxication were optimised for allyl alcohol, carbon tetrachloride, D-galactosamine and paracetamol. Silymarin extract, silychristin and silydianin did not exert cytotoxicity (10-100 microM), whereas silybin and isosilybin at higher concentrations and after longer incubation periods were cytotoxic. All main flavonolignans of silymarin tested displayed concentration-dependent cytoprotection against the toxic effects of both allyl alcohol and carbon tetrachloride but neither paracetamol nor galactosamine. The best protection was achieved by silydianin and silychristin and to a lesser degree by silymarin, while silybin and isosilybin were less effective. It is concluded that these differing outcomes result from the varying abilities of the Silybum marianum substances tested to stabilize the cell membrane, exert antioxidant properties and exhibit intrinsic toxicity.

Enhancement of allyl alcohol hepatotoxicity by endotoxin requires extrahepatic factors

Noninjurious doses of bacterial endotoxin (lipopolysaccharide; LPS) enhance allyl alcohol-induced liver damage in rats in a Kupffer cell (KC)-dependent fashion. To investigate the mechanism by which KCs contribute to liver injury in this model, isolated KCs and hepatocytes (HCs) were cocultured. Addition of LPS to the cocultured cells did not enhance allyl alcohol-induced cytotoxicity. In addition, recirculating perfusion of isolated livers from naïve rats with LPS for 2 h did not significantly enhance allyl alcohol-induced toxicity as measured by release of alanine aminotransferase (ALT). These results suggest an extrahepatic factor is required for LPS potentiation of allyl alcohol hepatotoxicity. To examine whether the coagulation cascade contributes to injury in this model, rats were given either warfarin at 42 and 18 h before LPS, or heparin at 1 h before LPS, and were treated with allyl alcohol 2 h after LPS. Warfarin and heparin each significantly blocked the decrease in plasma fibrinogen levels and attenuated the increase in plasma ALT activity in rats treated with LPS and allyl alcohol. To assess the role of thrombin in this injury, isolated livers from rats pretreated with LPS were perfused with thrombin or vehicle and allyl alcohol. Though LPS pretreatment enhanced the toxicity of allyl alcohol compared with livers from naïve rats, perfusion with thrombin did not increase sensitivity to allyl alcohol. In summary, LPS augments the hepatotoxicity of allyl alcohol through a mechanism involving extrahepatic factors, one of which may be a component of the coagulation cascade.

Modulation of hepatocyte thiol content by medium composition: implications for toxicity studies

Toxicity of compounds requiring glutathione for detoxification, thiol content and synthesis were determined in 24-h rat hepatocytes cultured in medium containing different concentrations of the sulphur amino acids. Glutathione synthesis was determined following prior depletion of glutathione with diethylmaleate. L-15 medium, which has high levels of cysteine and methionine (1 mM of each), provided some protection against dichloroacetone, dibromopropanol and dichloropropanol toxicity, and had a small effect on increasing glutathione content and synthesis, relative to Williams' medium E (WE) which has low levels (less than 0.5 mM) of both amino acids. However, WE containing N-acetylcysteine (NAC) (1 mM final cysteine concentration), with or without methionine (final concentration 1 mM), was a better cytoprotectant medium than L-15, markedly reducing toxicity of all three compounds, and rapidly (within 1.5 h) increasing cellular glutathione content. WE supplemented with methionine alone stimulated glutathione synthesis after an initial lag phase, and protected cultures against dichloropropanol, but not dibromopropanol or dichloroacetone, both of which are highly reactive in these cultures. There was a clear association between glutathione content at early time points in culture and toxicity observed at later time points, and overall these results indicate that differences in culture medium composition can alter intracellular glutathione content and xenobiotic toxicity.

Extensive protein carbonylation precedes acrolein-mediated cell death in mouse hepatocytes

Allyl alcohol hepatotoxicity is mediated by an alcohol dehydrogenase-derived biotranformation product, acrolein. This highly reactive alpha,beta-unsaturated aldehyde readily alkylates model proteins in vitro, forming, among other products, Michael addition adducts that possess a free carbonyl group. Whether such damage accompanies acrolein-mediated toxicity in cells is unknown. In this work we established that allyl alcohol toxicity in mouse hepatocytes involves extensive carbonylation of a wide range of proteins, and that the severity of such damage to a subset of 18-50 kDa proteins closely correlated with the degree of cell death. In addition to abolishing cytotoxicity and glutathione depletion, the alcohol dehydrogenase inhibitor 4-methyl pyrazole strongly attenuated protein carbonylation. Conversely, cyanamide, an aldehyde dehydrogenase inhibitor, enhanced cytotoxicity and protein carbonylation. Since protein carbonylation clearly preceded the loss of membrane integrity, it may be associated with the toxic process leading to cell death.

[Teratogenicity study of 2,2,3,3,3-pentafluoro-1-propanol (5FP) in rats by oral administration]

Teratogenicity of 2,2,3,3,3-pentafluoro-1-propanol (5FP), an alternative cleaning agent for chlorofluorocarbon, was examined in rats. 5FP was diluted with sesame oil and given to pregnant rats (Crj: Wistar) by gavage once a day from day 7 to 17 of pregnancy at doses of 0, 250, 500 and 1000 mg/kg/day. The pregnant rats were sacrificed on day 20 of pregnancy and their fetuses were examined for malformation. In the pregnant rats, 5FP caused wheezing, salivation, ptosis, reduced body weight gain and reduced food consumption at 500 and 1000 mg/kg/day. In the fetuses, 5FP reduced body weight, increased the incidences of skeletal variations and retarded the ossification at 1000 mg/kg/day, but did not increase the incidences of malformations. It was concluded from these results that 5FP has no teratogenicity in rats when given by gavage. The no-observed-adverse-effect level was 500 mg/kg/day for rat fetuses, and 250 mg/kg/day for pregnant rats.

Neoductular progenitor cells regenerate hepatocytes in severely damaged liver: a comparative ultrastructural study

In severely injured liver, stem cells give rise to progeny that tend to replace lost hepatocytes. Neoductular reaction appears as an inherent stage of liver reconstruction following severe damage caused by different pathological mechanisms. Few ultrastructural types of progenitor cells have been described, and some molecular phenotypes of progenitor stages have been characterized, but the details of the differentiation process are largely unknown. We prepared for light and electron microscopy examination human liver from biopsies of patients with chronic active hepatitis, and rat liver with allyl alcohol-induced periportal necrosis. We found that progenitor neoductular cells acquire the hepatocytic polarity pattern during a multi-step process apparently involving cell migration and dissolution of neoductular basement membrane. An intermediate stage with "mixed" ductular and hepatocytic polarity was described.

Insecticidal activity of essential oils: octopaminergic sites of action

A study was conducted to determine the insecticidal activity and mechanism of action of three essential oils (eugenol, alpha-terpineol and cinnamic alcohol) and an equal part mixture (3-blend) against American cockroaches (Periplaneta americana). To address species differences in response to treatment with the test oils, Carpenter ants (Camponotus pennsylvanicus De Geer), and German cockroaches (Blattella germanica) were included in this study. Exposed American cockroaches demonstrated hyperactivity followed by hyperextension of the legs and abdomen, then fast knockdown or quick immobilization followed by death. Ants and German cockroaches showed fast immobilization/knockdown followed by mortality. The 1:1:1 mixture (3-blend) was substantially effective against all test insects. One of the most remarkable observations was the increased frequency of heartbeats of American cockroaches in response to topical application of test oils. The changes in the pattern of cAMP level was biphasic. A significant increase in the cAMP level was found in response to 1 nmol/ml of eugenol, or 3-blend or 10 nmol/ml of alpha-terpineol. At higher concentrations a significant decrease in cAMP level was found. Blockage of octopamine receptors binding sites was also illustrated at lower concentrations of the test chemicals as judged by the decreased binding activity of [3H]octopamine to its receptors.

IN CONCLUSION

(1) test oils are neuro-insecticides and their insecticidal activity is species-dependent; (2) a synergistic effect of the three oils was found when they were equally mixed (3-blend); and (3) the octpaminergic system mediates the insecticidal activity of eugenol, alpha-terpienol and the 3-blend.

Clustering of hepatotoxins based on mechanism of toxicity using gene expression profiles

Microarray technology, which allows one to quantitate the expression of thousands of genes simultaneously, has begun to have a major impact on many different areas of drug discovery and development. The question remains of whether microarray analysis and gene expression signature profiles can be applied to the field of toxicology. To date, there are very few published studies showing the use of microarrays in toxicology and important questions remain regarding the predictability and accuracy of applying gene expression profiles to toxicology. To begin to address these questions, we have treated rats with 15 different known hepatotoxins, including allyl alcohol, amiodarone, Aroclor 1254, arsenic, carbamazepine, carbon tetrachloride, diethylnitrosamine, dimethylformamide, diquat, etoposide, indomethacin, methapyrilene, methotrexate, monocrotaline, and 3-methylcholanthrene. These agents cause a variety of hepatocellular injuries including necrosis, DNA damage, cirrhosis, hypertrophy, and hepatic carcinoma. Gene expression analysis was done on RNA from the livers of treated rats and was compared against vehicle-treated controls. The gene expression results were clustered and compared to the histopathology findings and clinical chemistry values. Our results show strong correlation between the histopathology, clinical chemistry, and gene expression profiles induced by the agents. In addition, genes were identified whose regulation correlated strongly with effects on clinical chemistry parameters. Overall, the results suggest that microarray assays may prove to be a highly sensitive technique for safety screening of drug candidates and for the classification of environmental toxins.

In vitro model using mouse hepatocytes for study of alcohol stress

In this study, the effects of ethanol and allyl alcohol on primary mouse hepatocytes were investigated. No cytotoxicity was observed by ethanol treatments, but more toxicity to cells was found in the response to allyl alcohol treatment. The expression of cytochrome P450 2E1 (CYP2E1), phase I enzyme was examined in response to ethanol and allyl alcohol. Both xenobiotics induced CYP2E1 up to 1.5 to approximately 5 fold at the protein level. The effects of insulin on CYP2E1 expression were also measured. Insulin, which has been regarded as an essential hormone for primary hepatocytes, was shown to decrease the level of CYP2E1 protein, and did not affect cell viability. These results on CYP2E1 induction demonstrate that primary mouse hepatocytes, when using ethanol and allyl alcohol as substrates and in insulin-free medium, provide a suitable system for the studies of the role of CYP2E1 in xenobiotic metabolism and toxicity.