sodium-nitrite and Cocarcinogenesis

Combined treatment with sodium nitrite (NaNO2) and ascorbic acid (AsA) has already been shown to promote rat forestomach carcinogenesis, possibly due to nitric oxide generation under acidic conditions. We hypothesized that a similar effect might occur in the esophagus when the luminal pH is decreased by acid reflux. To clarify this possibility, reflux esophagitis model rats (F344 male) were coadministered 0.2% NaNO2 in the drinking water and 1% AsA in the diet. After 32 weeks of the combined treatment, a significant increase in the incidence of epithelial hyperplasias of the lower-middle and lowest parts of the esophagus were observed compared with the basal-diet group, along with exacerbation of dysplasia and extension of the lesions. Additionally, one squamous cell papilloma was found only in the combined-treatment group. Subsequently, we confirmed the enhancing effects of NaNO2 and AsA cotreatment in the rat N-bis(2-hydroxypropyl)nitrosamine-initiated esophageal tumorigenesis model. The incidence of hyperplasia was enhanced in all segments, along with the incidence and multiplicity of squamous cell papillomas in the lowest segment of the esophagus. Thus, the data demonstrate that combined treatment with NaNO2 and AsA exerts promoting effects on rat esophageal carcinogenesis under acid reflux conditions, as in the forestomach. These findings suggest that the risk of excessive intake of a combination of nitrite and antioxidants for esophageal carcinogenesis is appreciable, particularly in patients with reflux esophagitis.

Topics: Animals; Antioxidants; Ascorbic Acid; Carcinoma, Squamous Cell; Cocarcinogenesis; Disease Models, Animal; Esophageal Neoplasms; Esophagitis, Peptic; Food Preservatives; Male; Rats; Rats, Inbred F344; Sodium Nitrite

Combination treatment with sodium nitrite (NaNO(2)) and ascorbic acid (AsA) is well known to promote forestomach carcinogenesis in rats and weakly enhance esophageal carcinogenesis under acid reflux conditions. Nitric oxide generation and oxidative DNA damage are considered to be related to the enhancement of carcinogenesis. The purpose of the present study was to investigate whether oxidative DNA damage-associated genotoxicity and tumor initiating potential are involved in the carcinogenesis. In the bacterial reverse mutation assay using Escherichia coli deficient in the mutM gene encoding 8-hydroxydeoxyguanosine (8-OHdG) DNA glycosylase, the combination with NaNO(2) and AsA increased the mutation frequency dramatically, slight increase being evident in the parental strain. In vivo, a significant increase in 8-OHdG levels in the rat forestomach epithelium occurred at 24 h after combined treatment. Six-week-old F344 male rats were given drinking water containing 0.2% NaNO(2) and a diet supplemented with 1% AsA in combination, or the chemicals individually or basal diet alone for 12 weeks. After an interval of 2 weeks, they received 1% butylated hydroxyanisole in the diet for promotion until the end of weeks 52 and 78. Although one squamous cell carcinoma was observed in the combined group, there was no significant variation in tumor development among the groups. The study indicated that the combination of NaNO(2) with AsA induces genotoxicity due to oxidative DNA damage in vitro, and elevates 8-OHdG levels in the forestomach epithelium, but lacks initiating activity in the rat two-stage carcinogenesis model.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Ascorbic Acid; Butylated Hydroxyanisole; Carcinogens; Cocarcinogenesis; Deoxyguanosine; Disease Models, Animal; DNA Damage; DNA, Bacterial; Drug Therapy, Combination; Escherichia coli; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mutagens; Organisms, Genetically Modified; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

Chronic sodium nitrite (SN) treatment potentiated spontaneous and 1,2-dimethylhydrazine (DMH)-induced carcinogenesis. Mice injected with SN alone showed a higher incidence of leukemia and lung cancer than in controls. Combined treatment with DMH and SN induced most of benign and malignant tumors (hepatic hemangioendothelioma, hepatocarcinoma, renal adenoma, etc.). The difference in the numbers of DMH- and SN-induced tumor bearers was not significant until a concentration of 500 mg/l was reached (64.7%). The level of multiple tumor incidence increased when SN 50 and 500 mg/l was used. Unlike DMH alone, cumulative incidence of DMH-specific tumors and leukemia after combined treatment was higher. An evaluation of cumulative incidence and relative risk established an indirect but positive correlation between SN dose, on the one hand, and spontaneous and induced carcinogenesis, on the other. The strongest carcinogenic effect was reported when DMH was used in combination with SN 500 mg/l. Our data confirmed the carcinogenic hazard of chronic exposure to SN which increased when in combination with that to a specific carcinogenic substance.

Topics: 1,2-Dimethylhydrazine; Animals; Carcinogens; Cocarcinogenesis; Drug Synergism; Leukemia; Lung Neoplasms; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Sodium Nitrite

The modifying effects of concurrent administration of fish meal and sodium nitrite on the development of renal tumors after initiation with N-ethyl-N-hydroxyethylnitrosamine (EHEN) were investigated. A total of 120 male 6-week-old Wistar rats were divided into six groups. Groups 1-3 (30 animals each) were given 1000 ppm EHEN in their drinking water for 3 weeks as an initiation treatment for renal cancer induction and thereafter fed respective diets containing 64, 32, and 8% (original concentration in the basal diet) fish meal, and simultaneously given 0.12% sodium nitrite in the drinking water for 33 weeks. Groups 4-6 (ten animals each) were similarly treated without the prior application of EHEN. At the end of the 37th experimental week, all surviving animals were autopsied and examined histopathologically for the existence of renal proliferative lesions. The incidences of dysplastic lesions, adenomas or adenocarcinomas of the kidney were not significantly different among groups 1-3. No renal proliferative lesions were found in groups 4-6. Chronic nephropathy was slightly but significantly enhanced in the 64 and 32% fish meal-treated groups as compared with group 3. Our results suggest that concurrent administration of fish meal and sodium nitrite does not affect the post-initiation phase of EHEN-induced renal carcinogenesis in the rat.

Topics: Adenocarcinoma; Adenoma; Adrenal Glands; Animals; Body Weight; Cocarcinogenesis; Diet; Diethylnitrosamine; Fish Products; Kidney; Kidney Neoplasms; Liver; Male; Organ Size; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Sodium Nitrite; Time Factors

N-nitroso-N-(2-hexanonyl)-3'-nitrotyramine (NO-HNTA) is a product generated in a model browning system in the presence of sodium nitrite. The chemical structure of this compound has been confirmed by UV, mass, nuclear magnetic resonance and infrared spectroscopy in our study. Twenty weeks, twice weekly, topical application of NO-HNTA at the concentration of 10, 50 and 250 mumol to mice previously initiated with benzo(a)pyrene (B[a]P) increased their tumor formation by 3.2-, 4.6- and 5.8-fold respectively. Application of the same amount of NO-HNTA not only caused significant induction of hyperplasia but also the activity of epidermal ornithine decarboxylase (ODC). Treatment of mouse skin with various amounts of NO-HNTA (10, 50 and 250 mumol) caused production of hydrogen peroxide by 1.38-, 1.95- and 3.26-fold respectively, and induction myeloperoxidase (MPO) by 24-, 63- and 102-fold. These results indicate that the formation of NO-HNTA or its derivatives derived from the reaction of tyrosine and glucose in the presence of sodium nitrite has the potential as a tumor promoter.

Topics: Animals; Benzo(a)pyrene; Carcinogens; Cocarcinogenesis; Dose-Response Relationship, Drug; Ear; Edema; Epidermis; Female; Hydrogen Peroxide; Magnetic Resonance Spectroscopy; Maillard Reaction; Mass Spectrometry; Mice; Ornithine Decarboxylase; Skin Neoplasms; Sodium Nitrite; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Tyramine

Aging effects on the susceptibility to chemical endometrial carcinogenesis were investigated in ICR female mice. The animals were divided into 3 groups of different ages: 1 month (young), 6 months (middle), and 12 months (old) at initiation of treatment. They received weekly oral administration of mixture of ETU (100 mg/kg body weight) and sodium nitrite (70 mg/kg body weight) for 6 months followed by a withdrawal period of 3 months. All animals were subjected to histopathology. The incidence of endometrial adenocarcinomas was highest in the middle age group (8/20), secondary in the old age group (4/20), and lowest in the young group (1/20). The incidence of atypical glandular hyperplasia, a precursor lesion of the tumor, was also higher in the middle age group. The endometrial adenocarcinomas showed morphological similarities among all age groups and the nuclei of tumor cells lost almost all staining reactivity to estrogen receptors. The labeling indices with bromodeoxyuridine (BrdU) were notably higher in the old age group than in the young and middle age groups. A further investigation on the aging process of female genital organs in control mice revealed that their senility seemed to be preceded by the formation of ovarian cysts which first appeared at 6 months of age with a concomitant elevation of plasma 17 beta-estradiol level. These results indicate that the susceptibility of the mouse endometrium to the carcinogenic effects of N-nitroso ETU could be closely linked with the stage of aging process of the genital organs and it appears to be most susceptible when initiated at around 6 months of age. However, the mitotic activity of neoplastic endometrial glandular cells seems to be higher in older mice than younger ones.

Topics: Administration, Oral; Age Factors; Animals; Cocarcinogenesis; Endometrial Neoplasms; Ethylenethiourea; Female; Mice; Mice, Inbred ICR; Sodium Nitrite

Endometrial carcinogenesis induced by concurrent oral administration of ethylenethiourea (ETU) and sodium nitrite (NaNO2) was investigated in ICR (Crj:CD-1) female mice. A mixed solution of ETU (100 mg/kg) and NaNO2 (70 mg/kg) was given to animals orally once a week for up to 6 months and all surviving animals were killed at 12 months of study. During the study, estrous cycle was monitored by vaginal smear and five or 10 selected animals were subjected to interim killing at 3 month interval to observe time-related carcinogenic responses of the uterus. Treatment with ETU and NaNO2 resulted in development of endometrial adenocarcinomas in the uterine horn and the incidence reached 42% in the surviving animals at 12 months. Prior to the development of the tumor, atypical hyperplasia of endometrial glands was frequently observed and regarded as the precancerous lesion. Immunohistochemistry for bromodeoxyuridine (BrdU) incorporation revealed higher labeling indices in both hyperplastic and neoplastic endometrial glandular cells, and the index in the adenocarcinoma was more than 20% on average at any stage of the estrous cycle. Overexpression of p53 protein, which is frequently demonstrated in virulent phenotypes of human corpus cancers, was seen in three out of eight (38%) adenocarcinomas, but not in the atypical hyperplasia or normal endometrial glands. There were no treatment-related changes in the estrous cycle on vaginal smears at any interval of the study. The analyses for plasma ovarian hormones at 12 months disclosed a marked depression of progesterone in the treated animals, while the 17 beta-estradiol (E2) level was comparable to the controls. These results suggest that endometrial carcinogenesis by ETU and NaNO2 could be initiated with atypical hyperplasia of the endometrial gland and a decrease in plasma progesterone level may play an important role in the development of endometrial carcinogenesis. In addition, inactivation of the p53 gene may play a significant role in the malignant transformation of endometrial epithelial cells in mice.

Topics: Adenocarcinoma; Administration, Oral; Animals; Bromodeoxyuridine; Cocarcinogenesis; Endometrial Neoplasms; Estrus; Ethylenethiourea; Female; Gonadal Steroid Hormones; Immunohistochemistry; Mice; Organ Size; Ovary; Sodium Nitrite; Tumor Suppressor Protein p53; Uterus; Vagina; Vaginal Smears

Carcinogenic potential of ethylenethiourea (ETU) in combination with sodium nitrite was investigated in ICR mice of both sexes. Groups of 30 males and 30 females each were given 10 weekly oral administrations of ETU and sodium nitrite with the following combinations of dosing (ETU vs sodium nitrite, mg/kg/wk): 0 vs 0, 100 vs 0, 0 vs 70, 25 vs 17.5, 50 vs 35, and 100 vs 70. Thereafter, the animals were allowed to live without treatment up to 18 mo after the first administration. Concurrent administration of ETU and sodium nitrite caused earlier development of tumors and/or dose-dependent increases in the incidences of tumors in the lymphatic tissue, lung, forestomach, Harderian gland, and uterus, whereas treatment with either ETU or sodium nitrite failed to show carcinogenic activity. In addition, carcinomas in the forestomach and uterine horn were limited to mice receiving concurrent administrations of ETU and sodium nitrite. These results indicate that ETU is most probably converted in vivo into N-nitroso ETU and that the N-nitroso ETU has a greater carcinogenic potential in mice than ETU alone.

Topics: Animals; Biotransformation; Carcinogens; Cocarcinogenesis; Ethylenethiourea; Female; Male; Mice; Mice, Inbred ICR; Neoplasms, Experimental; Sodium Nitrite

Effects of simultaneous treatment with NaNO2 and butylated hydroxyanisole, catechol, or 3-methoxycatechol were examined in a rat multiorgan carcinogenesis model. Groups of 15 animals were given a single i.p. injection of 100 mg/kg of body weight diethylnitrosamine, 4 i.p. injections of 20 mg/kg of body weight N-methylnitrosourea, 4 s.c. injections of 40 mg/kg of body weight dimethylhydrazine, p.o. treatment with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine in the drinking water for the first 2 weeks and p.o. treatment with 0.1% 2,2'-dihydroxy-di-n-propylnitrosamine in the drinking water for the next 2 weeks of the initial 4-week initiation period. Starting 3 days after the completion of these carcinogen treatments, animals were given diets containing 2% butylated hydroxyanisole, 0.8% catechol, 2% 3-methoxycatechol, or basal diet either alone or in combination with 0.3% sodium nitrite until week 28, when complete autopsy was performed. Histological examination showed that NaNO2 strongly enhanced development of forestomach lesions but inhibited that of glandular stomach lesions in rats simultaneously given catechol or 3-methoxycatechol with or without prior carcinogen exposure. 3-Methoxycatechol promoted esophageal carcinogenesis either with or without NaNO2, but promoting effects of catechol were evident only in the presence of NaNO2. In addition, treatment with NaNO2 after carcinogen exposure enhanced forestomach carcinogenesis. These results indicate that NaNO2 can modify phenolic antioxidant-induced cell proliferation and/or carcinogenesis, particularly in the upper digestive tract.

Topics: Animals; Antioxidants; Body Weight; Butylated Hydroxyanisole; Carcinoma in Situ; Carcinoma, Squamous Cell; Catechols; Cocarcinogenesis; Dimethylhydrazines; Disease Models, Animal; Drug Interactions; Eating; Epithelium; Hyperplasia; Liver; Male; Methylnitrosourea; Neoplasms, Experimental; Organ Size; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach; Stomach Neoplasms

It was shown in experiments on 186 mice that formation of tumors of the lung and fore-stomach induced by injection of sodium nitrite in combination with aminopyrine or methylurea is inhibited following treatment with ascorbic acid, hexamethylenetetramine or sodium metabisulfite.

Topics: Aminopyrine; Animals; Ascorbic Acid; Cocarcinogenesis; Female; Lung Neoplasms; Male; Methenamine; Methylurea Compounds; Mice; Mice, Inbred Strains; Nitrites; Sodium Nitrite; Stomach Neoplasms; Sulfites

Topics: Animals; Cocarcinogenesis; Drug Synergism; Female; Lung Neoplasms; Mammary Neoplasms, Experimental; Nitrates; Nitrites; Rats; Sodium Nitrite; Tritium; Water; Water Intoxication

In order to evaluate the effect of concurrent administration of areca nut and sodium nitrite, a long-term feeding study was conducted with 120 Syrian hamsters. The animals were divided into four treatment groups, each consisting of 15 males and 15 females, and received 2 g/kg diet of sodium nitrite (group I), 20 g/kg diet of powdered areca nut (group II), 2 g/kg diet of sodium nitrite plus 20 g/kg diet of areca nut (group III) or powdered diet only (group IV) throughout their lifetime. Urine samples from all groups were analysed for N-nitrosonipecotic acid (NNIP), a major urinary metabolite of areca-nut-derived nitrosamines. NNIP was only detected in the urine of hamsters fed nitrite plus areca nut (concentration: 1.9 +/- 0.9 ng/ml urine), indicating that areca nut alkaloids underwent in vivo nitrosation to form areca-nut-specific nitrosamines. The total tumour response was not significantly elevated in groups II and III. Hamsters of group III had a markedly, but also insignificantly higher frequency of malignant tumours than those of the other groups, with a statistically significant increase in malignant lymphomas in the males. Although limited by the low number of animals per group, these results indicate that exposure to nitrite together with areca nut constituents appears to enhance the risk of developing malignancies.

Topics: Animals; Areca; Biotransformation; Cocarcinogenesis; Cricetinae; Diet; Female; Male; Mesocricetus; Neoplasms, Experimental; Nipecotic Acids; Nitrites; Nitrosamines; Plant Extracts; Plants, Medicinal; Sex Factors; Sodium Nitrite

The concurrent administration of N-nitroso-N-methylbenzylamine (NMBA) (10 mg/l drinking water) and sodium nitrite (5 g or 1 g/kg basic diet) induces enhanced progression of esophageal tumors. Pathologic changes of the respiratory system, which do not occur with administration of NMBA alone, are also observed. These findings call for re-evaluation of the toxicological significance of nitrite.

Topics: Animals; Cocarcinogenesis; Dimethylnitrosamine; Drug Synergism; Esophageal Neoplasms; Female; Neoplasms, Experimental; Nitrites; Rats; Respiratory System; Sodium Nitrite

Topics: Animals; Cocarcinogenesis; Female; Male; Maternal-Fetal Exchange; Methylmercury Compounds; Neoplasms, Experimental; Nervous System Neoplasms; Nitrites; Pregnancy; Rats; Sodium Nitrite; Time Factors; Urea