Peter Bertinato

Bio: Peter Bertinato is an academic researcher from Dana Corporation. The author has contributed to research in topics: Propionitrile & Guanine. The author has an hindex of 4, co-authored 5 publications receiving 120 citations.

3-(Methylnitrosamino)propionitrile: Occurrence in Saliva of Betel Quid Chewers, Carcinogenicity, and DNA Methylation in F344 Rats

Abstract: 3-(Methylnitrosamino)propionitrile (MNPN), a potent carcinogen in F344 rats, was detected for the first time in the saliva of betel quid chewers at levels ranging from 0.5 to 11.4 micrograms/liter. The tumorigenic properties of MNPN and its potential to methylate DNA in F344 rats were evaluated. Groups of 21 male and 21 female rats were given 60 s.c. injections over a 20-week period (total doses 0.055 and 0.23 mmol per rat). The experiment was terminated after 106 weeks. MNPN at the higher dose induced 18 (86%) malignant tumors of the nasal cavity in male and 15 (71%) in female rats. The lower dose induced nine (43%) liver tumors. Groups of four or five male F344 rats were treated with a single s.c. or i.v. injection of MNPN (0.4 mmol/kg). MNPN was also administered to rats by swabbing the oral cavity (2.21 mmol/kg). The levels of 7-methylguanine and O6-methylguanine, formed 0.5-36 h after treatment, were measured in the liver, nasal mucosa, esophagus, and oral issues. The highest levels of methylated guanines were detected in the nasal cavity independent of the route of administration. The results of this study demonstrate that MNPN is present in the saliva of betel quid chewers and is a potent carcinogen in F344 rats.

Cyanoethylation of DNA in vivo by 3-(methylnitrosamino)propionitrile, an Areca-derived carcinogen.

Abstract: 2-Cyanoethyldiazohydroxide is a likely product of metabolic α-hydroxylation of 3-(methylnitrosamino)propionitrile (MNPN). The reaction of 2-( N -carbethoxy- N -nitrosamino)propionitrile, a stable precursor of 2-cyanoethyldiazohydroxide, with deoxyguanosine, catalyzed by porcine liver esterase, was investigated. Two major deoxyguanosine adducts were produced. They were isolated by high-performance liquid chromatography and characterized by their UV spectra, mass spectra, and proton magnetic resonance spectra. On the basis of these spectral data, the structures of the two adducts were assigned as 7-(2-cyanoethyl)guanine and O 6-(2-cyanoethyl)deoxyguanosine. The potential of MNPN to cyanoethylate DNA in F344 rats was evaluated by measuring 7-(2-cyanoethyl)guanine and O 6-(2-cyanoethyl)guanine in the liver, nasal mucosa, and esophagus. The highest levels were detected in the nasal cavity, which is one of the major target organs for the carcinogenic effects of MNPN.

Synthesis and kinetics of decomposition of 7-(2-cyanoethyl)guanine and O6-(2-cyanoethyl)guanine, markers for reaction of acrylonitrile and 3-(methylnitrosamino)propionitrile with DNA.

Abstract: Acrylonitrile, a carcinogen in rodents, is used in the large-scale production of acrylic polymers. 3-(Methylnitrosamino)propionitrile, a potent carcinogen in Fisher rats, is an Areca-derived nitrosamine which has been found in the saliva of betel quid chewers. Upon metabolic activation, both of these carcinogens can react with DNA to form 7-(2-cyanoethyl)guanine and O6-(2-cyanoethyl)guanine. The latter has never been described. We have therefore synthesized this derivative by reacting 2-(N-carbethoxy-N-nitrosamino)propionitrile with deoxyguanosine.

The role of N-(nitrosomethylamino)propionitrile in betel-quid carcinogenesis.

Abstract: N-(Nitrosomethylamino)propionitrile (NMAP) was isolated and identified in the saliva of betel-quid chewers in amounts ranging from 0.5 to 11.4 micrograms/l. Groups of 21 male and 21 female rats were given 60 subcutaneous injections of NMAP over a 20-week period (total doses, 0.055 and 0.23 mmol/rat). After 106 weeks, the higher dose had induced 18 (86%) malignant tumours of the nasal cavity in male and 15 (71%) in female rats. Nine (43%) liver tumours were observed among animals treated with the lower dose. Fischer 344 rats were treated with a single dose of NMAP (intravenously or subcutaneously, 0.4 mmol/kg; or by swabbing the oral cavity, 2.21 mmol/kg), and the levels of N7-methylguanine (7-meG) and O6-methylguanine (O6-meG) were measured in DNA isolated from oesophagus and nasal mucosa, which are target organs, and from liver which is not. Higher levels of O6-meG and 7-meG were detected in the nasal mucosa and lesser DNA methylation in the liver and oesophagus, independent of the mode of administration. This correlates with the results of the study of the tumorigenic properties of NMAP in rats.

Cyanoethylation of DNA in Vivoby 3-(Methylnitrosamino)propionitrile, an Areca-aeri\ed Carcinogen1

Abstract: Cyanoethyldiazohydroxide is a likely product of metabolic a-hy- droxylation of 3-(methylnitrosamino)propionitrile(MNPN). The reaction of 2-{Ar-carbethoxy-/V-nitrosamino)propionitrile, a stable precursor of 2- cyanoethyldiazohydroxide, with deoxyguanosine, catalyzed by porcine liver esterase, was investigated. Two major deoxyguanosine adducts were produced. They were isolated by high-performance liquid chromatogra- phy and characterized by their UV spectra, mass spectra, and proton magnetic resonance spectra. On the basis of these spectral data, the structures of the two adducts were assigned as 7-(2-cyanoethyl)guanine and 0'-(2-cyanoethyl)deoxyguanosine. The potential of MNPN to cyanoethylate DNA in F344 rats was evaluated by measuring 7-(2-cyanoethyl)guanine and 0'-(2-cyano- ethyl)guanine in the liver, nasal mucosa, and esophagus. The highest levels were detected in the nasal cavity, which is one of the major target organs for the carcinogenic effects of MNPN.

Tobacco-specific nitrosamines, an important group of carcinogens in tobacco and tobacco smoke

Abstract: Tobacco-specific nitrosamines are a group of carcinogens that are present in tobacco and tobacco smoke. They are formed from nicotine and related tobacco alkaloids. Two of the nicotine-derived nitrosamines, NNK and NNN, are strong carcinogens in laboratory animals. They can induce tumors both locally and systemically. The induction of oral cavity tumors by a mixture of NNK and NNN, and the organospecificity of NNK for the lung are particularly noteworthy. The amounts of NNK and NNN in tobacco and tobacco smoke are high enough that their total estimated doses to long-term snuff-dippers or smokers are similar in magnitude to the total doses required to produce cancer in laboratory animals. These exposures thus represent an unacceptable risk to tobacco consumers, and possibly to non-smokers exposed for years to environmental tobacco smoke. The permission of such high levels of carcinogens in consumer products used by millions of people represents a major legislative failure. Indeed, the levels of tobacco-specific nitrosamines in tobacco are thousands of times higher than the amounts of other nitrosamines in consumer products that are regulated by government authorities. Although the role of tobacco-specific nitrosamines as causative factors in tobacco-related human cancers cannot be assessed with certainty because of the complexity of tobacco and tobacco smoke, several lines of evidence strongly indicate that they have a major role, especially in the causation of oral cancer in snuff-dippers. Epidemiologic studies have demonstrated that snuff-dipping causes oral cancer. NNK and NNN are quantitatively the most prevalent known carcinogens in snuff, and they induce oral tumors when applied to the rat oral cavity. A role for NNK in the induction of lung cancer by tobacco smoke is likely because of its organospecificity for the lung. Tobacco-specific nitrosamines may also be involved in the etiology of tobacco-related cancers of the esophagus, nasal cavity, and pancreas. Because they are derived from nicotine, and therefore should be associated only with tobacco, tobacco smoke and other nicotine-containing products, tobacco-specific nitrosamines as well as their metabolites and macromolecular adducts should be ideal markers for assessing human exposure to, and metabolic activation of, tobacco smoke carcinogens. Ongoing research has demonstrated the formation of globin and DNA adducts of NNK and NNN in experimental animals. Sensitive methods for the detection and quantitation of these adducts in humans would provide an approach to assessing individual risk for tobacco-related cancers.(ABSTRACT TRUNCATED AT 400 WORDS)

Alert for an epidemic of oral cancer due to use of the betel quid substitutes gutkha and pan masala: a review of agents and causative mechanisms

Abstract: In south-east Asia, Taiwan and Papua New Guinea, smoking, alcohol consumption and chewing of betel quid with or without tobacco or areca nut with or without tobacco are the predominant causes of oral cancer. In most areas, betel quid consists of a mixture of areca nut, slaked lime, catechu and several condiments according to taste, wrapped in a betel leaf. Almost all habitual chewers use tobacco with or without the betel quid. In the last few decades, small, attractive and inexpensive sachets of betel quid substitutes have become widely available. Aggressively advertised and marketed, often claimed to be safer products, they are consumed by the very young and old alike, particularly in India, but also among migrant populations from these areas world wide. The product is basically a flavoured and sweetened dry mixture of areca nut, catechu and slaked lime with tobacco (gutkha) or without tobacco (pan masala). These products have been strongly implicated in the recent increase in the incidence of oral submucous fibrosis, especially in the very young, even after a short period of use. This precancerous lesion, which has a high rate of malignant transformation, is extremely debilitating and has no known cure. The use of tobacco with lime, betel quid with tobacco, betel quid without tobacco and areca nut have been classified as carcinogenic to humans. As gutkha and pan masala are mixtures of several of these ingredients, their carcinogenic affect can be surmised. We review evidence that strongly supports causative mechanisms for genotoxicity and carcinogenicity of these substitute products. Although some recent curbs have been put on the manufacture and sale of these products, urgent action is needed to permanently ban gutkha and pan masala, together with the other established oral cancer-causing tobacco products. Further, education to reduce or eliminate home-made preparations needs to be accelerated.

A framework for human relevance analysis of information on carcinogenic modes of action.

Abstract: The human relevance framework (HRF) outlines a four-part process, beginning with data on the mode of action (MOA) in laboratory animals, for evaluating the human relevance of animal tumors. Drawing on U.S. EPA and IPCS proposals for animal MOA analysis, the HRF expands those analyses to include a systematic evaluation of comparability, or lack of comparability, between the postulated animal MOA and related information from human data sources. The HRF evolved through a series of case studies representing several different MOAs. HRF analyses produced divergent outcomes, some leading to complete risk assessment and others discontinuing the process, according to the data available from animal and human sources. Two case examples call for complete risk assessments. One is the default: When data are insufficient to confidently postulate a MOA for test animals, the animal tumor data are presumed to be relevant for risk assessment and a complete risk assessment is necessary. The other is the product of a data-based finding that the animal MOA is relevant to humans. For the specific MOA and endpoint combinations studied for this article, full risk assessments are necessary for potentially relevant MOAs involving cytotoxicity and cell proliferation in animals and humans (Case Study 6, chloroform) and formation of urinary-tract calculi (Case Study 7, melamine). In other circumstances, when data-based findings for the chemical and endpoint combination studied indicate that the tumor-related animal MOA is unlikely to have a human counterpart, there is little reason to continue the risk assessment for that combination. Similarly, when qualitative considerations identify MOAs specific to the test species or quantitative considerations indicate that the animal MOA is unlikely to occur in humans, such hazard findings are generally conclusive and further risk assessment is not necessary for the endpoint-MOA combination under study. Case examples include a tumor-related protein specific to test animals (Case Study 3, d-limonene), the tumor consequences of hormone suppression typical of laboratory animals but not humans (Case Study 4, atrazine), and chemical-related enhanced hormone clearance rates in animals relative to humans (Case Study 5, phenobarbital). The human relevance analysis is highly specific for the chemical-MOA-tissue-endpoint combination under analysis in any particular case: different tissues, different endpoints, or alternative MOAs for a given chemical may result in different human relevance findings. By providing a systematic approach to using MOA data, the HRF offers a new tool for the scientific community's overall effort to enhance the predictive power, reliability and transparency of cancer risk assessment.

Tobacco-specific N-nitrosamines and Areca-derived N-nitrosamines : chemistry, biochemistry, carcinogenicity, and relevance to humans

Abstract: Nicotine and the minor tobacco alkaloids give rise to tobacco-specific N-nitrosamines (TSNA) during tobacco processing and during smoking. Chemical-analytical studies led to the identification of seven TSNA in smokeless tobacco (< or = 25 micrograms/g) and in mainstream smoke of cigarettes (1.3 micrograms TSNA/cigarette). Indoor air polluted by tobacco smoke may contain up to 24 pg/L of TSNA. In mice, rats, and hamsters, three TSNA, N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), are powerful carcinogens; two TSNA are moderately active as carcinogens; and two TSNA appear not to be carcinogenic. The TSNA are procarcinogens, agents that require metabolic activation. The active forms of the carcinogenic TSNA react with cellular components, including DNA, and with hemoglobin (Hb). The Hb adducts in chewers and smokers serve as biomarkers for the uptake and metabolic activation of carcinogenic TSNA and the urinary excretion of NNAL as free alcohol and as glucuronide for the uptake of TSNA. The review presents evidence that strongly supports the concept that TSNA contribute to the increased risk for cancer of the upper digestive tract in tobacco chewers and for the increased risk of lung cancer, especially pulmonary adenocarcinoma, in smokers. The high incidence of cancer of the upper digestive tract especially among men on the Indian subcontinent has been causally associated with chewing of betel quid mixed with tobacco. In addition to the TSNA, the betel quid chewers are exposed to four N-nitrosamines that are formed during chewing from the Areca alkaloids, two of these N-nitrosamines are carcinogens. The article also reviews approaches toward the reduction of the carcinogenic potency of smokeless tobacco, betel quid-tobacco mixtures, and cigarette smoke. Although the safest way to reduce the risk for tobacco-related cancers is to refrain from chewing and smoking, modifications of smokeless tobacco and of cigarettes are indicated to lead to less toxic products. Another more recent approach for reducing the carcinogenic effect of tobacco products is the application of chemopreventive agents, primarily of micronutrients. Future aspects in tobacco carcinogenesis, especially as it relates to TSNA, are expected in the field of molecular biochemistry and in biomarker studies, with the goal of identifying those tobacco and betel quid chewers and tobacco smokers who are at especially high risk for cancer.