Chemopreventive efficacy of a betel leaf extract against benzo[a]pyrene-induced forestomach tumors in mice.

The effect of betel leaf extract and some of its constituents, eugenol, hydroxychavicol, beta-carotene and alpha-tocopherol, on benzo[a]pyrene-induced forestomach neoplasia in male Swiss mice was examined. Betel leaf and its constituents decreased the number of papillomas per animal with the maximum protection, considering molar dosage, exhibited by beta-carotene and alpha-tocopherol. Except for beta-carotene, eugenol, hydroxychavicol and alpha-tocopherol increased the levels of reduced glutathione in the liver while glutathione S-transferase activity was enhanced by all except eugenol.

Carcinogenic potential of Indian alcoholic beverage (country liquor).

Epidemiological studies reveal that alcohol consumption is a risk factor for the cancer of the mouth, larynx, esophagus and various other organs. Of the various alcoholic beverages consumed in India, country liquors are widely consumed and that too by the economically weak section of the society. The present paper describes the experiments designed to investigate the effect of one brand of country liquor from Maharashtra State, India (which was found to be more potent in our earlier mutagenicity studies) for its carcinogenicity in two strains of mice and Syrian golden hamsters.

Carcinogenicity studies of tobacco extract in vitamin A-deficient Sprague-Dawley rats.

Long-term carcinogenicity studies were carried out in male Sprague-Dawley rats maintained on vitamin A-sufficient (SLO+) and vitamin A-deficient (SLO-) diets and treated with tobacco extract (TE). Three-week-old rats received by gavage a total dose of 860 mg of TE at a daily dose of 3 mg/rat over a period of 21 months. Besides tumorigenicity, drug-metabolizing phase I and phase II enzymes in lung and liver as well as vitamin A and C levels in plasma and liver were measured at 12 and 21 months of age.

Effect of 9,10-dimethyl-1,2-benzanthracene on the growth of hamster dermal fibroblasts in primary culture.

Newborn Syrian hamster dermal fibroblasts in primary culture have high plating efficiency, manifest as homogeneous contact-sensitive monolayer in mass cultures and above all possesses a short life-span of 15-20 days in culture. These cells are quite sensitive to mutagenic carcinogens. The DMBA treatment induced multi-layer and foci formation and growth in soft-agar suggesting that immortal variants can be obtained by treatment with carcinogens.

Mutagenicity and carcinogenicity of tea, Camellia sinensis.

Aqueous, caffeine free and tannin fractions of commercial tea and tannic acid were tested for mutagenicity in Ames test. Tea fractions of tannic acid were non mutagenic in strains TA 100, TA 98, TA 1535 and TA 1538 of Salmonella typhimurium with or without metabolic activation (rat-S9 mix) at different doses tested. In strain TA 98 the above tea fractions and tannic acid inhibited the S9 mix mediated mutagenicity of tobacco in a dose dependent manner.

Chemopreventive efficacy of betel leaf extract and its constituents on 7,12-dimethylbenz(a)anthracene induced carcinogenesis and their effect on drug detoxification system in mouse skin.

Effects of topically applied betel leaf extract (BLE) and its constituents. beta-carotene, alpha-tocopherol, eugenol and hydroxychavicol on 7,12-dimethylbenz(a)anthracene (DMBA) induced skin tumors were evaluated in two strains of mice. BLE, beta-carotene and alpha-tocopherol, significantly inhibited the tumor formation by 83, 86, 86% in Swiss mice and 92, 94 and 89% in male Swiss bare mice respectively.

Species differences in hepatic pulmonary and upper gastrointestinal tract biotransformation enzymes on long-term feeding of masheri--a pyrolyzed tobacco product.

The activities of several activating enzymes and that of glutathione S-transferase as well as levels of glutathione were measured in the upper alimentary tract, lung, and liver of Swiss mice, Sprague-Dawley rats, and Syrian golden hamsters treated with 10% masheri (pyrolyzed tobacco) in diet for 20 months. Significant increase in activities of phase I activating enzymes and a remarkable decrease in the phase II detoxification system in most extrahepatic tissues of the treated animals of all three species was observed. These observations suggest that the prolonged exposure to environmental xenobiotics/carcinogens affects the drug-metabolizing enzymes of the gastrointestinal tract, which may be an important factor in determining the susceptibility of different organs to carcinogen exposure.

Species difference in intestinal drug metabolising enzymes in mouse, rat and hamster and their inducibility by masheri, a pyrolysed tobacco product.

Activities of several drug metabolising enzymes in the small intestine were investigated in Swiss mice, Sprague Dawley rats and Syrian Golden Hamsters fed 10% masheri, a pyrolysed tobacco product, in diet, for 20 months. The basal levels of enzymes in proximal (PI), medium (MI) and distal (DI) parts of the intestine in the three species were similar. However, the levels of cytochrome P-450, benzo(a) pyrene hydroxylase (B(a)OH) and glutathione S-transferase (GST) were highest in hamsters followed by rat and mice.

Electron microscopic changes on the DMBA induced oral precancerous and cancerous lesion in hamster cheek pouch.

Experiments were performed to study the early and late ultrastructural changes during hamster cheek pouch carcinogenesis using a regimen of topical application of 9,10 dimethyl-1-1-2 benzanthracene (DMBA) twice a week in liquid paraffin oil. The DMBA was administered for a period of 2 and 4 1/2 months. Hamsters exposed to DMBA for 2 months developed moderate precancerous changes, whereas the hamsters treated with DMBA for 4 1/2 months developed frank and multiple oral tumors with a cauliflower appearance.

Carcinogenicity studies of masheri: pyrolysed tobacco product, in vitamin-A-deficient Sprague Dawley rats.

The carcinogenicity of long-term feeding of masheri extract to animals in a vitamin-A-sufficient (SLO+) and deficient (SLO-) state was studied in Sprague Dawley rats by feeding daily dose of 3 mg extract over a period of 21 months. The phase I activating enzymes, the glutathione (GSH)/glutathione S-transferase (GST) detoxification system, and the hepatic and circulating levels of vitamins A and C were also monitored at 12 and 21 months. It was observed that the phase I enzyme activities were significantly higher in SLO+ than in SLO- rats at both 12 months and 21 months.

Effect of long-term treatment of two tobacco-specific N-nitrosamines on the vitamin A status of mice.

The effect of long-term treatment of two important tobacco-specific N-nitrosamines, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), on the depot or circulating levels of vitamin A of Swiss and BALB/c male mice was studied. It was observed that treatment of both NNN and NNK in Swiss and BALB/c mice decreased liver vitamin A levels significantly. NNK treatment also caused a decrease in the levels of vitamin A in plasma.

Effect of vitamin A status of rats on metabolizing enzymes after exposure to tobacco extract or N'-nitrosonornicotine.

The effects of N'-nitrosonornicotine (NNN) and tobacco extract on hepatic and pulmonary biotransformation enzymes were studied in rats fed vitamin A-sufficient or -deficient for semisynthetic diets. Basal levels of cytochrome P450, benzo[a]pyrene hydroxylase, benzphetamine demethylase, glutathione S-transferase and glutathione were lower in the group on the deficient diet. Treatment with tobacco extract or NNN significantly increased the levels of these enzymes in the sufficient diet group.

Antimutagenic and anticarcinogenic effects of betel leaf extract against the tobacco-specific nitrosamine 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK).

Earlier studies showed that betel leaf inhibits the mutagenic action of standard mutagens like benzo[a]pyrene and dimethylbenz[a]anthracene. Since tobacco-specific nitrosamines are the major carcinogens present in unburnt forms of tobacco, we studied the effect of an extract of betel leaf on the mutagenic and carcinogenic actions of one of the most potent, 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK). Betel-leaf extract and hydroxychavicol suppressed the mutagenicity of NNK in both the Ames and the micronucleus test.

Activation of N'-nitrosonornicotine by hydrogen peroxide in vitro.

Betel-quid ingredients were found to produce reactive oxygen species, such as superoxide anion and hydrogen peroxide, in vitro. We demonstrated that N'-nitrosonornicotine (NNN) can be converted to its active metabolite, hydrogen peroxide, nonenzymatically in the presence of ferrous ions and ethylenediaminetetracetic acid (EDTA) at pH 7.2.

Inhibitory effects of snuff extract on ornithine decarboxylase and aryl hydrocarbon hydroxylase activities in relation to cell proliferation of mouse tongue epithelial cells.

Effect of snuff extract (SE) on cell proliferation as measured by 3H thymidine (TdR) uptake, induction of ornithine decarboxylase (ODC) and aryl hydrocarbon hydroxylase (AHH) was studied in primary embryonal mouse tongue cultures. Cultures treated with SE in combination with 7,12-dimethylbenz(a)anthracene (DMBA) showed inhibition of cell proliferation and decrease of ODC and AHH activities, compared to control, DMBA, and DMBA + 12-O-tetradecanoylphorbol 13-acetate treated cultures.

Modulation of Masheri- and benzo[a]pyrene-inducible carcinogen-metabolizing enzymes by dietary vitamin A.

The modulatory role of dietary vitamin A on the carcinogen metabolizing enzymes was studied in masheri extract and benzo[a]pyrene-treated rats. Weanling male Sprague-Dawley rats were fed vitamin A deficient (SR-) and vitamin A sufficient (SR+) semisynthetic diets for 12 weeks. ME/B[a]P treatment significantly increased the phase I activating enzymes in both SR- and SR+ groups.

Effect of nutritional status on mutagenicity of urine excreted by rats treated with standard/experimental carcinogens.

Urine samples, collected from Sprague Dawley rats treated with extracts of tobacco/masheri, benzo (a) pyrene, N'-nitrosonornicotine, N'-nitrosodiethylamine and maintained on semi-synthetic diets sufficient or deficient in Vitamin A, B and protein were tested for mutagenicity using Salmonella/microsome assay. The mutagenic activity of urine or various treated groups was in the order deficient diet greater than standard laboratory diet greater than nutritionally sufficient diet. Present results confirmed the earlier observations that nutritionally deficient animals are likely to have more exposure to mutagenic metabolites that are generated by increased phase I enzymes and decreased detoxification system.

Effect of tobacco extract and N'-nitrosonornicotine on the carcinogen metabolising enzymes under different dietary vitamin B status.

Studies were carried out to evaluate the changes in the phase I and II enzymes of xenobiotic metabolism, on treatment with tobacco extract (TE) and a tobacco specific carcinogen, N'-nitrosonornicotine (NNN) in Sprague-Dawley rats maintained on vitamin B complex sufficient and deficient semi-synthetic diets. Both TE and NNN significantly increased the hepatic and pulmonary phase I enzymes in the vitamin B sufficient (SB+) and deficient (SB-) animals. However, the percent increase in enzyme activities was drastically higher in the SB- treated group as compared to those in the SB(+)-treated group.

Chemical analysis of smoke of Indian cigarettes, bidis and other indigenous forms of smoking--levels of steam-volatile phenol, hydrogen cyanide and benzo(a)pyrene.

Levels of steam-volatile phenol, hydrogen cyanide and benzo(a)pyrene in various types of tobacco smoking products marketed in the country have been determined for the first time. Steam-volatile phenol levels in six popular brands of Indian cigarettes varied from 118 to 226 micrograms, and in six popular brands of bidis, from 129 to 273 micrograms. Cheroot and cigarillos yielded 400 micrograms and 333 micrograms steam-volatile phenol respectively.

Modulatory effects of snuff, retinoic acid, and beta-carotene on DMBA-induced hamster cheek pouch carcinogenesis in relation to keratin expression.

The hamster cheek pouch (HCP) serves as an excellent model system not only for the studies on initiation and promotion but also for the modulation of experimental oral carcinogenesis. In our studies, HCPs treated with 7,12-dimethylbenz[a]anthracene (DMBA) showed both cheek pouch and stomach papillomas. Utilizing this model system, we tested and compared the modulatory effects of snuff, retinoic acid, and beta-carotene on the incidence of tumors and the keratin expression pattern.

Total particulate matter and nicotine in Indian bidis and cigarettes: a comparative study of standard machine estimates and exposure levels in smokers in Bombay.

Standard emission levels of total particulate matter (TPM) and nicotine in bidi and cigarette smoke were compared with exposure levels based on smoking behaviour of smokers in Bombay. Bombay cigarette smokers are getting much higher amount of carcinogenic dry TPM (28 to 79%) and nicotine (31 to 104%), compared to standard machine estimates. In the case of regular bidi (60 mm) harmful ingredients like dry TPM decreased from 11 to 15 percent and nicotine increased from 11 to 22 percent, whereas long bidi (80 mm) delivered higher amount of dry TPM (14 to 22%) and nicotine (33 to 37%) in smokers in Bombay compared to standard machine estimates.

Carcinogenicity studies on the two tobacco-specific N-nitrosamines, N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco-specific N-nitrosamines (TSNA) have been implicated in oral cancer. However, except for one study using rats, no study has shown the ability of TSNA in inducing oral tumours in experimental animals. We have studied the carcinogenic potentials of N'-nitrosonornicotine (NNN) and 4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in mice and hamsters, wherein the nitrosamines were administered on the tongues of the mice and the cheek pouches of the hamsters to simulate the exposure conditions of humans.

Carcinogenic tobacco-specific nitrosamines in Indian tobacco products.

Various Indian tobacco products--cigarette, bidi, chutta and their smoke, chewing tobacco and snuff (used for inhalation as well as a dentifrice) were analysed for their content of tobacco-specific nitrosamines (N'-nitrosonornicotine, 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone and N'-nitrosoanatabine) by means of a gas chromatograph interfaced with a thermal energy analyser. These tobacco-specific nitrosamines were detected at microgram/g levels in all products investigated and in ng quantities in tobacco smoke. The highest concentrations were in chutta tobacco and snuff used for inhalation.

Mutagenic and cytogenetic studies of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco specific nitrosamines (TSNA) N'-nitrosonornicotine (NNN) and 4-(Methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) were tested for mutagenic and clastogenic effects using a battery of short-term test systems. These test systems include the Ames test, micronucleus test (MNT), induction of chromosomal aberrations and sister chromatid exchange (SCEs). NNN and NNK were tested for their potency in inducing mutations in the Ames Salmonella/microsome assay and their clastogenic action were tested by the micronucleus inducing ability in vivo using Swiss mice.