DNA adducts from alkoxyallylbenzene herb and spice constituents in cultured human (HepG2) cells.

Alkoxy derivatives of allylbenzene, including safrole, estragole, methyleugenol, myristicin, dill apiol, and parsley apiol, are important herb and spice constituents. Human exposure occurs mainly through consumption of food and drinks. Safrole, estragole, and methyleugenol are weak animal carcinogens.

Effects of NQO1 deficiency on levels of cyclopurines and other oxidative DNA lesions in liver and kidney of young mice.

I-compounds are bulky indigenous DNA adducts that can be detected by (32)P-postlabeling. A subgroup, termed type II I-compounds, represents DNA lesions induced by oxidative stress. Several major type II I-compounds have been identified as dinucleotides containing 3'-terminal 8,5'-cyclo-2'-deoxyadenosine (cA).

Effects of dietary transition metals on oxidative DNA lesions in neonatal rats.

Bulky endogenous oxidative lesions (type II I-compounds) reflect DNA damage associated with oxidative stress. As shown by 32P-postlabeling, their levels are enhanced by pro-oxidant genotoxins and also shortly after normal birth in several rat tissues as a function of time and the maternal diet. In order to elucidate which dietary components contribute to postnatal DNA damage, we have focused, herein, on the possible role of transition metals (iron, copper, and nickel).

A 32P-postlabeling assay for the oxidative DNA lesion 8,5'-cyclo-2'-deoxyadenosine in mammalian tissues: evidence that four type II I-compounds are dinucleotides containing the lesion in the 3' nucleotide.

8,5'-Cyclopurine-2'-deoxynucleotides, which are strong blocks to mammalian DNA and RNA polymerases, represent a novel class of oxidative DNA lesion in that they are specifically repaired by nucleotide excision repair but not by base excision repair or direct enzymatic reversion. Previous studies using thin layer chromatography of (32)P-postlabeled DNA digests have detected several bulky oxidative lesions of unknown structure, called I-compounds, in DNA from normal mammalian organs. We investigated whether any of these type II I-compounds contained 8,5'-cyclo-2'-deoxyadenosine (cA).

Effects of different diets and dietary restriction on perinatal endogenous DNA adducts. Time dependence of oxidative and presumptive nonoxidative lesions.

Type II I-compounds (indigenous DNA adducts) denote a class of bulky oxidative DNA lesions that are detectable by 32P-postlabeling and represent useful biomarkers of DNA damage induced by oxidative stress. Their levels are increased in tissue DNA under pro-oxidant conditions, for example, as previously shown, in newborn rat organs. Here we have investigated whether the maternal diet affects perinatal type II I-compound levels.

Acute elevation by short-term dietary restriction or food deprivation of type I I-compound levels in rat liver DNA.

Type I I-compounds are bulky endogenous DNA modifications detectable by 32P postlabeling that exhibit age, species, tissue, genotype, gender, and diet dependence. Their formation appears unrelated to oxidative stress. In fact, several lines of indirect evidence suggest that many type I I-compounds may represent normal functional DNA modifications.

Genotoxicity of complex PAH mixtures recovered from contaminated lake sediments as assessed by three different methods.

Although human exposure generally occurs to mixtures of chemicals, limited toxicological information is available to characterize the potential interactions of the components of environmental mixtures. This study was conducted to compare the genotoxicity of chemically characterized polycyclic aromatic hydrocarbon (PAH) mixtures using in vitro and in vivo techniques. A total of three extracts (E1-E3) were selected from sediment samples collected from a lake adjacent to an abandoned coal gasification site.

Bulky endogenous DNA modifications (I-compounds) -possible structural origins and functional implications.

I-compounds are bulky covalent DNA modifications which increase with age in tissues of unexposed laboratory animals and are derived from endogenous DNA-reactive intermediates of nutrient and oxygen metabolism. They have been classified into 2 major groups, i.e.

Endogenous formation and significance of 1,N2-propanodeoxyguanosine adducts.

The detection of 1,N2-propanodeoxyguanosine adducts in the DNA of rodent and human tissues as endogenous lesions has raised important questions regarding the source of their formation and their roles in carcinogenesis. Both in vitro and in vivo studies have generated substantial evidence which supports the involvement of short- and long-chain enals derived from oxidized polyunsaturated fatty acids (PUFAs) in their formation. These studies show that: (1) the cyclic propano adducts are common products from reactions of enals with DNA bases; (2) they are formed specifically from linoleic acid (LA; omega-6) and docosahexaenoic acid (omega-3) under in vitro stimulated lipid peroxidation conditions; (3) the levels of propano adducts are dramatically increased in rat liver DNA upon depletion of glutathione; (4) the adduct levels are increased in the liver DNA of the CCl4-treated rats and the mutant strain of Long Evans rats which are genetically predisposed to increased lipid peroxidation; and (5) adduct levels are significantly higher in older rats than in newborn rats.

High levels of endogenous DNA adducts (I-compounds) in pig liver. Modulation by high cholesterol/high fat diet.

I (indigenous)-compounds are bulky endogenous DNA adducts which are detected by 32P-postlabeling in unexposed animals. I-compound levels in rodents depend on age, species, strain, gender, tissue, diet, and chemical exposure. There are two classes of I-compounds, type I and type II.

Partial characterization of two major liver I-compounds as unstable adducts which are readily hydrolyzed to unmodified guanine nucleotides.

I-compounds are endogenous bulky DNA modifications which are detected by nuclease P1-enhanced 32P-post-labeling in tissue DNA of animals not knowingly exposed to carcinogens. Their profiles and levels depend inter alia on animal age, species, strain, tissue, gender, diet and exposure to chemicals such as cytochrome P450 inducers and carcinogens. Due to lack of sufficient material obtainable from in vivo sources, chemical structures of I-compounds and their parent normal bases have not yet been identified.

Inhibition of CYP1A1-dependent activity by the polynuclear aromatic hydrocarbon (PAH) fluoranthene.

Polynuclear aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants, and recently bioassay-based induction studies have been used to determine exposures to complex mixtures of PAHs. Induction of CYP1A1-dependent activity in H4IIE rat hepatoma cells has been used extensively as a bioassay for halogenated aromatic hydrocarbons and more recently for PAHs. Fluoranthene (FL) is a prevalent PAH contaminant in diverse environmental samples, and FL did not induce CYP1A1-dependent ethoxyresorufin O-deethylase (EROD) activity significantly in H4IIE cells.

Comparison of immunoaffinity chromatography enrichment and nuclease P1 procedures for 32P-postlabelling analysis of PAH-DNA adducts.

32P-postlabelling analysis for detecting DNA adducts formed by polycyclic aromatic compounds is one of the most widely used techniques for assessing genotoxicity associated with these compounds. In cases where the formation of adducts is extremely low, a crucial step in the analysis is an enrichment procedure for adducts prior to the radiolabelling step. The nuclease P1 enhancement procedure is the most established and frequently used of these methods.

Enhanced levels in neonatal rat liver of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-hydroxydeoxyguanosine), a major mutagenic oxidative DNA lesion.

The purpose of this study was to determine whether the level of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-hydroxy-2'-deoxyguanosine) (8-oxo-dG), a major mutagenic DNA oxidation product, is enhanced in newborn rat liver DNA as a consequence of oxidative stress incurred during the early postnatal period. 32P-postlabeling showed this adduct to increase approximately 2-fold from the 20th day of gestation (2 days before birth) to a peak level at 50-53 h after birth. Postnatal levels exceeded fetal levels at all time points investigated, i.

Organ-specific oxidative DNA damage associated with normal birth in rats.

Mammalian DNA contains bulky endogenous DNA modifications (I-compounds), which increase with age in unexposed animals, as shown by 32P-postlabeling. We have examined the perinatal formation of a subclass (type II) of I-compounds in rat liver, kidney, skin and lung. These I-compounds represent bulky oxidative DNA lesions, defined herein as intrastrand base-base and base-sugar cross-links, adducts of lipid peroxidation products and DNA-protein cross-links.

Effects of cytochrome P450 inducers on tamoxifen genotoxicity in female mice in vivo.

We recently reported that administration of the antiestrogen tamoxifen (TAM) gives rise to two groups of DNA adducts in female mouse liver in vivo, as measured by 32P-postlabeling, and provided evidence that 4-hydroxytamoxifen and alpha-hydroxytamoxifen are proximate carcinogenic metabolites leading to group I and group II adducts, respectively (Randerath et al., Carcinogenesis 15: 2087-2094, 1994). Because cytochrome P450 (CYP) enzymes play an important role in TAM metabolism, in this investigation we tested the hypothesis that induction of liver CYP enzymes may affect TAM metabolism profoundly, resulting in increased or decreased TAM-DNA adduct formation in vivo.

Comparative 32P-postlabeling analysis of exogenous and endogenous DNA adducts in mouse skin exposed to a wood-preserving waste extract, a complex mixture of polycyclic and polychlorinated chemicals.

Wood preserving waste (WPW) sites contain numerous toxic compounds, including phenols, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins, and dibenzofurans. Previous in vitro and in vivo 32P-postlabeling studies showed the induction of multiple carcinogen-DNA adducts by WPW extracts. We now have tested the hypothesis in a mouse skin bioassay that a WPW extract not only causes the formation of exogenous, xenobiotic-derived DNA adducts, but also alters the levels of endogenous DNA modifications.

DNA adducts and chronic degenerative disease. Pathogenetic relevance and implications in preventive medicine.

Chronic degenerative diseases are the leading causes of death in developed countries. Their control is exceedingly difficult due to their multiplicity and diversity, the interconnection with a network of multiple risk factors and protective factors, the long latency and multistep pathogenesis, and the multifocal localization. Adducts to nuclear DNA are biomarkers evaluating the biologically effective dose, reflecting an enhanced risk of developing a mutation-related disease more realistically than the external exposure dose.

Organ-specific oxidative DNA damage associated with normal birth in rats.

Mammalian DNA contains bulky endogenous DNA modifications (I-compounds), which increase with age in unexposed animals, as shown by 32P-postlabeling. We have examined the perinatal formation of a subclass (type II) of I-compounds in rat liver, kidney, skin and lung. These I-compounds represent bulky oxidative DNA lesions, defined herein as intrastrand base-base and base-sugar cross-links, adducts of lipid peroxidation products and DNA-protein cross-links.

Monophosphate 32P-postlabeling assay of DNA adducts from 1,2:3,4-diepoxybutane, the most genotoxic metabolite of 1,3-butadiene: in vitro methodological studies and in vivo dosimetry.

Among the main DNA-reactive metabolites of 1,3-butadiene (BD), both 1,2:3,4-butadiene diepoxide (BDE) and 1,2-epoxy-3-butene (BME) have been reported in mice and rats exposed to BD, but blood and tissue levels of these metabolites are much higher in mice than in rats under similar exposure conditions. BDE, being more reactive and genotoxic than BME, is thought to be responsible for the greater susceptibility of mice to BD carcinogenicity. While BDE is a DNA-alkylating agent and some BDE adducts have been characterized, no sufficiently sensitive method has been reported for studying BDE-DNA binding in vivo.

32P-postlabeling of 1,3-butadiene and 4-vinyl-1-cyclohexene metabolite-DNA adducts: in vitro and in vivo applications.

Epoxides of 1,3-butadiene, i.e. 1,2-epoxy-3-butene and 1,2:3,4-diepoxybutane are DNA-reactive metabolites.

In vitro and in vivo (32)P-postlabeling analysis of 4-vinyl-1-cyclohexene (butadiene dimer) diepoxide-DNA adducts.

4-Vinyl-1-cyclohexene diepoxide (VCD), and industrial chemical, and its parent compound, 4-vinyl-1-cyclohexene (VCH), are potential health hazards, a they destroy oocytes in follicles in rodents. VCD is also a skin carcinogen at the site of application in both female and male mice and rats and after gavage, induces ovarian tumors in mice and forestomach tumors in rats. A (32)P-postlabeling assay was developed for the detection and measurement of VCD-DNA adducts.

Structural origins of bulky oxidative DNA adducts (type II I-compounds) as deduced by oxidation of oligonucleotides of known sequence.

Bulky DNA adducts, previously termed type II I-compounds, are detected by 32P-postlabeling following treatment of DNA with several Fenton-type oxygen radical-generating reagents, i.e., mixtures of Fe(II) or Ni(II) and H2O2.