Tumorigenic agents in unburned processed tobacco: N-nitrosodiethanolamine and 1,1-dimethylhydrazine

Analysis of hydrazine in smokeless tobacco products by gas chromatography-mass spectrometry

Background

Due to the lower health risks associated with the use of certain categories of smokeless tobacco products (STPs) such as Swedish snus, there is interest in the comparative levels of toxic chemical constituents in different types of STPs. A method has been developed and validated for the analysis of hydrazine in STPs. Seventy four commercial STPs from the US and Sweden, representing 80-90% of the 2010 market share for all the major STP categories in these two countries, as well as three reference STPs, were analysed for hydrazine.

Results

Aqueous extracts of the STPs were treated with excess pentafluorobenzaldehyde (PFB), which reacted with hydrazine in solution to form decafluorobenzaldehyde azine (DFBA). DFBA was partitioned into hexane and then quantified by gas chromatography–mass spectrometry (GC–MS). The method was validated using five different types of STP, was linear in the range 8–170 ng/mL, and had limits of quantification (LOQ) from 26–53 ng of hydrazine per g of STP (as sold). The method was applied to the analysis of 74 contemporary STPs commercially available in the United States and Sweden, none of which were found to contain hydrazine above the LOQ or LOD. Trace levels of compounds showing chromatographic and mass spectral features consistent with hydrazine were identified at very low levels (sub-limit of detection, <10 ng/g) in the chromatograms of less than half of the 74 STPs examined; in contrast, for 40 of the STPs no evidence for the presence of hydrazine was observed. Where present, the levels of compounds consistent with hydrazine were estimated to be at least an order of magnitude lower than the only previous study to have quantified hydrazine in tobacco.

Conclusions

Our results show that hydrazine is not a prevalent constituent of STPs, and when present is not quantifiable using currently available analytical methodology.

Detection and simultaneous quantification of three smoking-related ethylthymidine adducts in human salivary DNA by liquid chromatography tandem mass spectrometry

Smoking cigarette increases levels of certain ethylated DNA adducts in certain tissues and urine. Cigarette smoking is a major risk factor of various cancers and DNA ethylation is involved in smoking-related carcinogenesis. Among the ethylated DNA adducts, O(2)-ethylthymidine (O(2)-edT) and the promutagenic O(4)-ethylthymidine (O(4)-edT) are poorly repaired and they can accumulate in vivo. Using an accurate, highly sensitive, and quantitative assay based on stable isotope dilution nanoflow liquid chromatography-nanospray ionization tandem mass spectrometry (nanoLC-NSI/MS/MS), O(2)-edT, N(3)-edT (N(3)-ethylthymidine), and O(4)-edT adducts in human salivary DNA were simultaneous detected and quantified. Saliva is easily accessible and available and it can be a potential target in searching for noninvasive biomarkers. Under the highly selected reaction monitoring (H-SRM) mode, salivary samples from 20 smokers and 13 nonsmokers were analyzed. Starting with 50 μg of DNA isolated from about 3.5 mL of saliva, levels of O(2)-edT, N(3)-edT, and O(4)-edT in 20 smokers' salivary DNA samples were 5.3±6.2, 4.5±5.7, 4.2±8.0 in 10(8) normal nucleotides, respectively, while those in 13 nonsmokers were non-detectable. In addition, statistically significant correlations (p<0.0001) were observed between levels of O(2)-edT and N(3)-edT (γ=0.7388), between levels of O(2)-edT and O(4)-edT (γ=0.8839), and between levels of N(3)-edT, and O(4)-edT (γ=0.7835). To the best of our knowledge, this is the first report of detection and quantification of these three ethylthymidine adducts in human salivary DNA, which might be potential biomarkers for exposure to ethylating agents and possibly for cancer risk assessment.

Natural products containing a nitrogen-nitrogen bond

As of early 2013, over 200 natural products are known to contain a nitrogen-nitrogen (N-N) bond. This report categorizes these compounds by structural class and details their isolation and biological activity.

Mutagenicity of alkylhydrazine oxalates in Salmonella typhimurium TA100 and TA102 demonstrated by modifying the growth conditions of the bacteria

Alkylhydrazines are important carcinogens. However, they show generally only weak mutagenicity and the activities reported from different laboratories are contradictory. We have developed a sensitive method to detect the mutagenicity of alkylhydrazines. The method is based on a modified preculturing procedure in the Ames test, the emphasis in the modification being a change in the growth period of tester strains. The optimal growth periods were found to be 11 h in Salmonella typhimurium TA100 and 5 h in Salmonella typhimurium TA102. We tested the mutagenic activity of 12 alkylhydrazines; 1,2-dimethylhydrazine, 1,2-diethylhydrazine, 1,2-dipropylhydrazine, 1,2-dibutylhydrazine, 1,1-dimethylhydrazine, 1,1-diethylhydrazine, 1,1-dipropylhydrazine, 1,1-dibutylhydrazine, methylhydrazine, ethylhydrazine, propylhydrazine and butylhydrazine. All 12 alkylhydrazines were clearly mutagenic in Salmonella typhimurium TA102, and 10 hydrazines were mutagenic in Salmonella typhimurium TA100, both in the absence of S9 mix. The mutagenicity was inhibited by the addition of S9 mix or bovine serum albumin. This suggests deactivation of the mutagens by proteins.

The in vitro and in vivo effects of 1,1-dimethylhydrazine (UDMH) on murine lymphocyte subsets and Ia antigen expression

1,1-Dimethylhydrazine or unsymmetrical dimethylhydrazine (UDMH) is a highly volatile and reactive compound used primarily as a liquid rocket propellant. Previous studies found UDMH to possess immunomodulatory activity similar to other hydrazine derivatives. Modulation of T lymphocyte subpopulations and Major Histocompatibility Complex Class II or Ia antigen were evaluated as possible mechanisms for this UDMH-induced immunomodulation. Murine lymphoid cell populations were examined by flow cytometry for changes in their cell surface marker percentages or relative number upon exposure to UDMH either in vitro or in vivo. The results show UDMH caused significant suppression of the T helper cell population derived from the thymus at the 75 mg/kg dose in vivo, but did not affect other lymphocyte subpopulations isolated from mesenteric lymph node, spleen or thymus at this or any other dose. In vivo exposure of mice at all doses of UDMH did not significantly alter expression of Ia antigens on adherent cell populations and expression of the Ia antigen following in vitro UDMH exposure was not affected as well. Results indicate that the immunomodulatory effects of UDMH are not mediated by phenotypic alteration of T lymphocyte subpopulations or Ia antigen.

Effect of lifetime administration of dimethylaminoethanol on longevity, aging changes, and cryptogenic neoplasms in C3H mice

The effects of lifetime treatment with dimethylaminoethanol on longevity and cryptogenic neoplasm formation were studied in females of two mouse sub-lines, the C3H/HeN which carries a germinal mammary tumor provirus and the C3H/HeJ(+) which also carries the exogenous mammary tumor virus. Administration in the drinking water of 10 mM dimethylaminoethanol to the C3H/HeN mice or 15 mM to the C3H/HeJ(+) mice did not result in significant differences between treated and untreated groups in average survival. No changes in age-related organ structure or morphology were observed with dimethylaminoethanol treatment, except for an apparent decrease in the amount of lipofuscin in the liver judged in histological sections. Among untreated C3H/HeJ(+) females, 89% developed neoplasms of the mammary gland, ovary, liver, lung and reticuloendothelial system, while the incidence was 88% in the treated mice. In C3H/HeN females, neoplasms of the mammary gland, ovary, liver, lung and lymphatic system occurred in 57% and in 60% of treated mice. Also, there was no statistically significant difference between control and treated animals in the age of onset or the type of specific neoplasms. Dimethylaminoethanol did not induce any neoplasms.

Induction of malignant peripheral nerve sheath tumors in European hamsters with 1,1-dimethylhydrazine (UDMH)

A rate of up to 43% of malignant peripheral nerve sheath tumors (PNST) was induced in European hamsters (EH) after weekly s.c. administration of 1,1-dimethylhydrazine (UDMH). The overall neoplastic response in the treated EH was also elevated as compared to the untreated controls. Histologically, the malignant PNST were neurofibrosarcomas and melanotic as well as unpigmented schwannomas. The occurrence of melanotic schwannomas is briefly discussed with regard to the histogenesis of this rare tumor type.

Genetic activity of the carcinogen N-nitrosodiethanolamine (NDELA) on unstable mutant alleles of the white locus in Drosophila melanogaster

The genetic activities of the carcinogen N-nitrosodiethanolamine (NDELA) were assayed somatically and germinally on two stocks carrying unstable alleles of the white (w+) eye colour gene: one incorporating a TE (z TE w+; coded UZ), the other with a tandem duplication of part of the encoding w+ sequence (wi16). Treatment was applied topically on late embryonic and early larval stages over a wide dose range (0.01-2.0 M) and the general mutagenic levels actually achieved were measured in terms of the X-recessive mutations (lethals and visibles) recovered in Muller-5 tests on samples of the males scored for somatic sectoring. The carcinogen was germinally ineffective on the z TE w+ and wi16 loci even at the maximal tested dose (2.0 M), and was only weakly mutagenic with respect to the X-recessives (lethals + visibles) at massive doses (1.0-2.0 M). In contrast, it proved to be genetically effective somatically, inducing red eye sectors through regulatory effects involving the TE in the UZ stock and complete reversion to w+ in the case of wi16 at comparatively moderate doses (less than or equal to 0.26 M). The possible implications of the demonstration of the genetic activity of NDELA in the soma to the carcinogenic process, and to the wider problem of screening for environmental genotoxic compounds, are discussed.

Free radical metabolism of hydralazine. Binding and degradation of nucleic acids

The binding of hydralazine, a hydrazine-containing hypotensive drug, to nucleic acids has been studied. Binding of this drug to biopolymers was assayed using spin-trapping techniques in the presence of various metal ions, which produce free radical intermediates from hydralazine [B. K. Sinha and A. G. Motten, Biochem, biophys. Res. Commun. 105, 1044 (1982)]. Some interaction was detected with the single-stranded nucleic acids. Hydralazine binds strongly to the native DNA, most likely by intercalation of the drug into DNA bases. In the presence of nucleic acids and metal ions, hydralazine stimulated the production of OH(.) radicals which was inversely proportional to the degree of binding. Aldehyde formation in DNA was also induced by hydralazine which was stimulated by superoxide dismutase and inhibited by catalase.

Identification of an acidic metabolite of N-nitrosodiethanolamine isolated from rat urine

N-Nitrosodiethanolamine metabolism was studied in order to clarify the mechanism(s) by which this compound elicits its carcinogenic effect. Samples of 24 h urine from rats given a single dose of N-nitrosodiethanolamine were collected. Gas chromatographic thermal energy analyses showed the presence of only one compound containing the nitroso moiety besides N-nitrosodiethanolamine. This compound was identified as the acidic derivative N-(2-hydroxyethyl)-N-carboxymethylnitrosamine by comparison with an authentic standard by means of gas chromatographic mass spectrometric analysis of the trimethylsilyl or pentafluorobenzyl esters. The amount of N-(2-hydroxyethyl)-N-carboxymethylnitrosamine excreted in the 24 h urine was about 6% of the N-nitrosodiethanolamine administered.

A review of environmental and health risks of maleic hydrazide

The cellular metabolism, acute toxicity, mutagenicity, and carcinogenicity of maleic hydrazide have been reviewed. It seems that this chemical is a mutagen and a carcinogen in cell cultures and animals, but no evidence is available on human carcinogenicity regardless of population exposure in manufacturing, agriculture, and the food chain (i.e., potatoes, potato chips). Because of the level of exposure of the general public to this compound, an epidemiologic survey should be conducted to ascertain possible human health effects. Long-term feeding experiments should be conducted in several animal species to establish whether maleic hydrazide is carcinogenic by this route. Biotransformation and pharmacokinetic studies should be undertaken to obtain better understanding of the chemical's metabolism and excretion. Such investigations would firmly establish whether the tolerance for maleic hydrazide should remain unchanged or whether the use of the compound should be more restricted.

Tumorigenicity of minute dose levels of N-methyl-N-formylhydrazine of Gyromitra esculenta

Separate administrations of 0.0005 to 0.00025% N-methyl-N-formylhydrazine in drinking water to 6-week-old randomly bred Swiss mice for the remainder of their lifetime induced lung neoplasms. At the high dose level, 64% of the females and 48% of the males developed lung tumors, while the corresponding tumor incidences at the lower dose level were 62% in the females and 54% in the males. In untreated controls, the lung tumor incidences were 29% in the females and 19% in the males. Histopathologically, the lesions were classified as adenomas and adenocarcinomas of the lungs. N-methyl-N-formylhydrazine is a stable constituent of the edible false morel mushroom Gyromitra esculenta. The environmental significance is discussed, in view of the carcinogenicity of minute doses of this chemical.

Studies of the tumorigenic potential of 4-substituted phenylhydrazines by the subcutaneous route

4-Methylphenylhydrazine hydrochloride (4-MPH) was administered to randomly bred Swiss mice as 26 weekly sc injections of 140 microgram per gram of body weight and N'-acetyl-4-(hydroxymethyl)phenylhydrazine (AMPH) as 26 weekly sc injections of 500 microgram/g. As a solvent control, physiological saline was also given as 26 weekly sc injections of 0.01 ml/g. The 4-MPH treatment induced a significant incidence (24%) of fibrosarcomas in males. In the 4-MPH-treated females and some AMPH-treated male mice, a few soft-tissue tumors were observed; however, their appearance could not be related to treatment. 4-MPH is formed under special experimental conditions from 4-hydroxymethylphenyl-hydrazine, which is an in vitro breakdown product of agaritine, an ingredient of the cultivated mushroom Agaricus bisporus. The implications of the findings are discussed.

Tumorigenesis by N-n-propyl-N-formylhydrazine in mice

Continuous administration of 0.04% N-n-propyl-N-formylhydrazine (PFH) for life in drinking water to 6-week-old randomly bred Swiss mice induced tumours of the lungs, preputial glands, liver and gallbladder. The tumour incidences in these 4 tissues were 91, 22, 8 and 6%, whereas in the untreated controls they were 25, 0, 0.5 and 0.5%, respectively. The higher dose of 0.08% PFH, given under identical conditions, induced only tumours of the lungs, liver and gall bladder in low incidences, since the compound was too toxic for the mice. Histopathologically, the tumours were classified as adenomas and adenocarcinomas of the lungs, squamous-cell papillomas, and carcinomas and fibrosarcoma of preputial glands, benign hepatomas and liver-cell carcinoma, as well as adenomas and adenocarcinoma of the gall bladder. The investigation is part of our structure/activity relationship inquiry aimed at revealing the mechanism of action of the N-alkyl-N-formylhydrazine series of chemicals.

Mutagenicity of marijuana and Transkei tobacco smoke condensates in the Salmonella/microsome assay

Extracts and smoke condensates of marijuana, Transkei home-grown tobacco and also commercial cigarette tobaccos were assayed for their mutagenic activity to Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and TA1538, both with and without metabolic activation. No mutagenic activity was detected in dichloromethane extracts of marijuana and tobacco per se, but all the smoke condensates exhibited mutagenicity with metabolic activation. The only strain not mutated by any of the pyrolyzates was TA1535. Transkei tobacco pyrolyzate proved to be the most mutagenic, followed by marijuana, pipe and cigarette tobacco. Mutagenicity was positively associated with the nitrogen content of the various products. The potent mutagenic action of marijuana smoke condensate, coupled with a condensate yield of more than 50% higher than that of cigarette and pipe tobacco, indicates a high carcinogenic risk associated with marijuana smoking.

Hydrazines as mutagens in a histidine-requiring auxotroph of Salmonella typhimurium

Hydrazines have been found naturally in tobacco and mushrooms. Other hydrazines are used in industry, medicine, and agriculture. Although about 38 hydrazines are carcinogenic, few, if any, have been tested successfully in rapid bacterial mutagenesis assays. We have utilized a tester strain of Salmonella typhimurium (TA1530) in order to determine the mutagenic activity of a number of hydrazines and related compounds. This strain is thus shown to be effective as a tester organism for the facile detection of hydrazines as mutagens.

Formylhydrazine carcinogenesis in mice

Administration of 0.125% formylhydrazine in drinking water to 6-week-old randomly bred Swiss albino mice for life, induced lung tumours. Compared to untreated controls, the lung-tumour incidence rose from 15 to 94% in the females and from 22 to 100% in the males. The treatment had no detectable tumorigenic effect in other organs.

Urinary excretion of N-nitrosodiethanolamine administered orally to rats

N-Nitrosodiethanolamine (NDE1A) was administered by gavage to male rats in single doses of 1000, 500 and 100 mg/kg body wt. More than 70% of a given dose was excreted unchanged in the urine, essentially within the first 24 h after exposure. This high excretion rate might explain the relatively low carcinogenic potential of NDE1A, and also offers a possible method of monitoring exposure to this compound under occupational and/or environmental conditions.

Effects of N-nitrosodiethanolamine and 1,1-diethanolhydrazine in Syrian golden hamsters

N-Nitrosodiethanolamine (NDEA) and 1,1-diethanolhydrazine (DEH) were synthesized and injected subcutaneously weekly in male and female Syrian golden hamsters. The total NDEA dose per hamster was approx. 15 g/kg body wt. applied in either 7 or 27 subdoses. DEH was administered in 78 applications to two groups yielding total doses of 1.1 g and 273 mg/kg body wt. Under these conditions, DEH did not show a specific demonstrable carcinogenic effect. However, within 78 weeks after the first application, 39 out of 56 hamsters treated with NDEA developed tumors. Primarily, neoplasms of the nasal cavity and tracheal tumors were observed, as well as a few hepatocellular adenomas and sarcomas at the injection site. These findings and those of the earlier study on carcinogenicity of NDEA in rats raise concern as to the safety for human consumption or industrial use of products with the potential for forming NDEA.

The large bowel carcinogenic effects of hydrazines and related compounds occurring in nature and in the environment

Five substituted hydrazines that induce large bowel and other types of cancer in laboratory animals are described. Two of these compounds, which originate in nature, are 1,1-dimethylhydrazine, a tobacco ingredient, and methylhydrazine, formed from a chemical present in the edible wild mushroom Gyromitra esculenta. The human population is therefore exposed to them considerably. In addition, both compounds are manufactured and used in rocket fuel. The other three chemicals, 1,2-dimethylhydrazine dihydrochloride,1-methyl-2-butylhydrazine dihydrochloride and trimethylhydrazine hydrochloride, are manufactured synthetically only and apparently are not found in substantial quantities in the environment.

Tumorigenic effect of 4-methylphenylhydrazine hydrochloride in Swiss mice

4-Methylphenylhydrazine hydrochloride was administered as 10 weekly subcutaneous injections of 140 microgram/g body weight and as 7 weekly intragastric instillations of 250 microgram/g body weight in physiological saline to randomly bred Swiss mice. Treatments given subcutaneously resulted in induction of lung tumors in incidences of 36% in females and 44% in males, while intragastric treatment caused a 40% incidence in females. In addition, it gave rise to blood vessel tumors by intragastric route in incidences of 32% in females and 18% in males. In the two physiological saline-treated control groups, the lung tumor incidence (combined) was 20% in females and 21% in males, while the blood vessel tumor incidence (combined) was 7% in females and 6% in males. Histopathologically, the lesions were classified as adenomas and adenocarcinomas of the lungs, and angiomas and angiosarcomas of blood vessels. 4-Methylphenylhydrazine was postulated to be a metabolite of 4-hydroxymethylphenylhydrazine, an ingredient of the commonly eaten mushroom Agaricus bisporus. The implications are discussed with respect to the tumorigenesis data.

Mutagenicity of smoke condensates from cigarettes, cigars and pipe tobacco

Smoke condensates from cigarettes, cigars and pipe tobacco were mutagenic on Salmonella typhimurium TA100 and TA98 when activated with rat liver microsomal system. Mutagenicity of a unit weight of smoke condensate was rather high in cigars, low in pipe tobacco and intermediate in cigarettes. Specific mutagenic activity was almost comparable among smoke condensates from low- to high-tar cigarettes, although some variations were observed depending upon the country producing the cigarettes. Marked mutagenicity of cigarette smoke condensate could not be explained by the benzo (a) pyrene or nitroso compounds it actually contained, suggesting the presence of other very potent mutagens in tobacco smoke condensates.