Mutagenicity studies on N-nitrosated products of the Maillard browning reaction: N-nitroso-fructose-amino acids

Role of Nitric Oxide-Derived Metabolites in Reactions of Methylglyoxal with Lysine and Lysine-Rich Protein Leghemoglobin

Carbonyl stress occurs when reactive carbonyl compounds (RCC), such as reducing sugars, dicarbonyls etc., accumulate in the organism. The interaction of RCC carbonyl groups with amino groups of molecules is called the Maillard reaction. One of the most active RCCs is α-dicarbonyl methylglyoxal (MG) that modifies biomolecules forming non-enzymatic glycation products. Organic free radicals are formed in the reaction between MG and lysine or Nα-acetyllysine. S-nitrosothiols and nitric oxide (^•NO) donor PAPA NONOate increased the yield of organic free radical intermediates, while other ^•NO-derived metabolites, namely, nitroxyl anion and dinitrosyl iron complexes (DNICs) decreased it. At the late stages of the Maillard reaction, S-nitrosoglutathione (GSNO) also inhibited the formation of glycation end products (AGEs). The formation of a new type of DNICs, bound with Maillard reaction products, was found. The results obtained were used to explain the glycation features of legume hemoglobin-leghemoglobin (Lb), which is a lysine-rich protein. In Lb, lysine residues can form fluorescent cross-linked AGEs, and ^•NO-derived metabolites slow down their formation. The knowledge of these processes can be used to increase the stability of Lb. It can help in better understanding the impact of stress factors on legume plants and contribute to the production of recombinant Lb for biotechnology.

Fructose consumption during pregnancy and lactation causes DNA damage and biochemical changes in female mice

The consumption of fructose during pregnancy can cause hyperglycaemia and may stimulate production of reactive oxygen species; however, there are only a few studies reporting whether fructose consumption during pregnancy causes DNA damage. Therefore, the aim of this study was to evaluate the effects of fructose consumption on genetic and biochemical parameters in Swiss mice treated during pregnancy and lactation. For this, 15 couples of 60-day-old Swiss mice were divided into three groups of five couples: negative control (water) and two fructose groups (fructose dose of 10%/l and 20%/l). During this period, we evaluated food consumption, energy efficiency and body weight. Samples of blood were collected from the females before copulation, after the 15th day of conception and on the 21st day after the lactation period, for the glycaemic and lipid profiles as well as comet assay and micronucleus (MN) test. Comet assay and MN test evaluate DNA damage and clastogenicity, respectively. In the gestation and lactation period, the two fructose doses tested showed DNA damage as observed in the comet assay, which is associated with an increase in dietary intake, body weight, lipid profile and fasting glycaemia in females. Thus, it can be suggested that the high consumption of fructose during these periods is harmful for pregnancy and lactation.

A comparative study of the mutagenicity of various types of tobacco products

Toxicological data are an important aspect of tobacco product characterization. In this study, TPM (Total Particulate Matter) (three replicates) was collected from cigarettes [five brands, ISO conditions: puff volume, 35 mL; duration, 2s; interval, 60s (35/2/60)], cigars (two brands, 45/2/30), cigarillos (two brands, 35/2/60), bidis (two brands, 45/2/30), and pipe tobacco (two brands, 50/2/12). TPM was extracted from the Cambridge filter pad using dimethyl sulfoxide (DMSO). Smokeless tobacco (ST) (six brands) was extracted with DMSO using an ultrasonic homogenizer. Both types of extracts were filtered and stored at -80 degrees C. All extracts were analyzed for humectants, water and nicotine. Mutagenic activity was assessed per OECD guideline 471 using Salmonella typhimurium TA98+S9 and TA100+S9. TA98+S9 response (specific activity expressed as revertants/mg nicotine) was greatest for the cigarette fabricated with dark, air-cured tobaccos. Average product responses with TA98+S9 based on nicotine and relative to cigarettes (excluding dark tobacco) were cigars, 242%; cigarillos, 238%; bidis, 91%; and pipe tobacco, 44%. ST response was not significant for TA98+S9. Corresponding values for TA100+S9 were cigars, 189%; cigarillos, 155%; pipe tobacco, 130%; bidis, 114% and ST, 34%. ST TA100+S9 response ranged from a low of 501 to a high of 8547 revertants/mg nicotine, depending on ST composition.

Total N-nitroso compounds and their precursors in hot dogs and in the gastrointestinal tract and feces of rats and mice: possible etiologic agents for colon cancer

We review evidence that red and processed meat are causes of colon cancer and that processed meat is a risk factor for childhood cancer and type 2 diabetes. Associations could be due to N-nitroso compounds (NOCs) derived from nitrosation of NOC precursors (NOCPs). We review our survey of total NOC and NOCP content of foods. Only rapidly nitrosated amines, including a glycosyl amino acid, were efficiently determined as NOCPs. NOCPs in hot dogs and rat feces were partly purified by adsorption-desorption and HPLC. After nitrosation, purified hot dog fractions were directly mutagenic in Ames test. The main NOCPs in these materials may be N-glycosyl amino acids and peptides. NOC levels in rat gastrointestinal tract rose steadily from stomach to feces. NOCP levels showed similar trend but with sharp increases from stomach to duodenum. One day after Min and C57BL/6J mice were fed 4% dextran sulfate sodium to induce acute colitis, fecal NOC levels increased 1.9-fold compared with untreated mice (P < 0.05). For 7 d Swiss mice received semipurified diet, 180 g beef-pork hot dogs mixed with 820 g diet or 180 g sautéed beef mixed with 820 g diet. Fecal NOC outputs on day 7 were 3.7-5.0 (hot dog) and 2.0-2.9 (beef) times those for control groups (P < 0.002 for combined groups), perhaps reflecting higher dietary NOC intakes. Feeding a similar hot dog mixture to mice did not affect normal 7-methyldeoxyguanosine level in colonic mucosal DNA. Overall, results support the hypothesis that colonic NOCs are a cause of colon cancer.

Tumor promotion of N-nitroso-N-(3-keto-1, 2-butanediol)-3'-nitrotyramine derived from nitrosation of Maillard reaction product in CD-1 mice

N-Nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (NO-NTA) is a product of a model browning system generated in the presence of sodium nitrite. Our previous study showed that NO-NTA had genotoxicity and proved to be an initiator and promoter on mouse C3H10T1/2 cells. In this study, a two-stage skin carcinogenesis protocol was used to promote CD-1 mouse skin carcinogenesis using NO-NTA. Twice weekly, for 38 weeks, topical application of NO-NTA at the concentration of 250 nmol to mice previously initiated with benzo(a)pyrene (BaP) caused 90% tumor incidence. However, no tumors were observed in mice treated with BaP or treated with NO-NTA alone. The NO-NTA-promoted tumors that were observed histologically in mice showed well-differentiated squamous cell carcinoma with invasion into the subcutaneous region. Application of the same amount of NO-NTA not only caused significant induction of hyperplasia but also epidermal ornithine decarboxylase (ODC) activity. Treatment of mouse skin (1 cm(2)) with various amounts of NO-NTA (10, 50, or 250 nmol) caused production of hydrogen peroxide by 1.63-, 1.91-, and 2. 38-fold, respectively, and marked induction of myeloperoxidase (MPO) by 21-, 39-, and 61-fold. These results indicate that NO-NTA is a new tumor promoter and may induce tumor promotion by oxidant stress in CD-1 mouse skin.

Tumor promoting effect of N-nitroso-N-(2-hexanonyl)-3'-nitrotyramine (a nitrosated Maillard reaction product) in benzo(a)pyrene-initiated mouse skin carcinogenesis

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.

Promotional effect of N-nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (a nitrosated Maillard reaction product) in mouse fibroblast cells

N-Nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (NO-NTA) is a product of model browning system generated in the presence of sodium nitrite. The chemical structure of this compound has been confirmed by UV, mass and nuclear magnetic resonance, and infrared spectroscopy in our previous study. A two-stage transformation protocol was used to chemically transform the mouse embryo fibroblasts C3H10T1/2 cells. To initiate transformation, the cells were treated with benzo[a]pyrene (BaP) (0.1 mg/ml), and NO-NTA (0.01, 0.1 and 1 mg/ml) was employed subsequently to complete the transformation process. Malignant transformed foci were formed in BaP-initiated and NO-NTA promoted C3H10T1/2 cells after 8 wk. Cells treated with NO-NTA alone failed to induce transformation. However, cells initiated with BaP and promoted by cells initiated with BaP and promoted by NO-NTA demonstrated oncogenic properties. Cell lines transformed with NO-NTA-transformed colonies exhibited enhanced growth rate, anchorage independence and tumorigenicity in animals relative to parent cells. These results indicate that NO-NTA is a new tumour promoter and may induce tumour promotion by two-stage oncogenesis. Further studies on the mechanism of action of NO-NTA are now in progress.

N-Nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine. A new genotoxic agent derived from the reaction of tyrosine and glucose in the presence of sodium nitrite

N-Nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (NO-NTA) is a product of a model browning system in the presence of sodium nitrite. In this study, the chemical structure is confirmed by spectral studies, including UV, mass spectrometry, nuclear magnetic resonance and infrared spectroscopy. NO-NTA is strongly genotoxic to the rat hepatocyte and is moderately cytotoxic to mouse C3H10T1/2 cells. Results obtained in this study indicate that NO-NTA inflicted DNA damage through the formation of a DNA adduct. In addition, C3H10T1/2 cells were treated with NO-NTA and, following addition of 12-O-tetradecanoylphorbol-13-acetate (TPA) as promotor, the increase of transformed foci indicated that NO-NTA could possibly be an initiator [corrected] of TPA tumor promotion. A transformed cell line from NO-NTA initiated and TPA promoted foci increased saturation density and growth ability in soft agar reactive to the control line. These results suggest that the formation of a genotoxic agent of nitroso-derivatives may take place in a nitrite-containing food system during processing and cooking.

In the search for new anticancer drugs. XXV: Role of N-nitrosated amadori compounds derived from glucose-amino acid conjugates in cancer promotion or inhibition

Earlier investigators found that some N-nitrosated Amadori compounds, derived from glucose and amino acid condensation reactions, exhibit mutagenic properties and theorized that these potentially carcinogenic compounds might be formed in the human digestive system. To further investigate these compounds, N-nitrosated Amadori compounds [i.e., N-(1-deoxy-D-fructos-1-yl)-L-N-nitroso-glycine (5a), -threonine (5b), -methionine (5c), -valine (5d), -phenylalanine (5e), and -tryptophan (5f)] were synthesized by modifications of known methods. Acute toxicity tests of 5a, 5b, 5c, 5d, 5e, and 5f in male Swiss mice produced the following lowest lethal limits of toxicity: 2000, 2000, 4000, 3000, 2000, and 6000 mg/kg, respectively, whereas the highest tolerated doses were 1750, 1500, 3000, 1500, and 5000 mg/kg, respectively. The 50% lethal dose (intraperitoneally) for 5b in mice was approximately 1777 mg/kg. This value is at least three times higher than that for the over-the-counter drug ibuprofen (i.e., 495 mg/kg, intraperitoneally, in mice). Compounds 5b, 5c, 5d, and 5f were evaluated in vitro by the National Cancer Institute primary antitumor screen consisting of 60 cell lines. None of the four compounds caused a significant inhibition of cell growth, even at the maximum dosage of 10(-4) M. Compounds 5a-f were tested in vivo against the lymphocytic leukemia P388, and 5b and 5f were tested against the lymphoid leukemia L1210 in CDF1 male mice following the National Cancer Institute protocol. There were no significant differences in results between the control and drug-treated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of the occurrence and formation of non-volatile N-nitroso compounds in foods

A review of the literature published prior to July 1991 covers the occurrence and formation of non-volatile N-nitrosamines occurring in foods and beverages. The presence of identified volatile and non-volatile N-nitrosamines accounts for less than 10% of the total apparent N-nitrosamine concentration. N-Nitrosoproline and N-nitrosothiazolidine-4-carboxylic acid are the most commonly identified non-volatile N-nitrosamines in the diet. Non-volatile N-nitrosamines account for 12 of the 21 currently identified N-nitroso compounds in foods and beverages.

Nutritional and toxicological aspects of the Maillard browning reaction in foods

The Maillard, or nonenzymatic, browning reaction between carbonyl and amino groups is a common reaction in foods which undergo thermal processing. The Maillard reaction is a desirable consequence of many industrial and domestic processes and is responsible for the attractive flavor and brown color of some cooked foods. An early recognized consequence of the Maillard reaction was the destruction of some essential amino acids, such as lysine. More recently, research interest has focused on the production of toxic and antinutritive compounds. This review examines the nutritional and toxicological consequences of the Maillard reaction in light of the findings of such research. In particular, the effect of Maillard reaction products on the digestion, absorption, and excretion of nutrients is considered. The cytotoxicity, mutagenicity, and immunochemical aspects of selected Maillard reaction products are also examined and suggestions are made for future areas of investigation.

Synthesis, structure-activity relationships and a reaction mechanism for mutagenic N-nitroso derivatives of glycosylamines and Amadori compounds--model substances for N-nitrosated early Maillard reaction products

A series of nine glycosylamines and an Amadori compound were synthesized, together with their N-nitroso derivatives. Their structures were established by physico-chemical and spectroscopic data and elemental analyses. The N-nitroso compounds were further characterized by denitrosation with hydrogen bromide-acetic acid, followed by detection of the liberated NO by a chemiluminescence detector. N-Nitroso derivatives of N-p-nitrophenyl/p-methylphenyl/p-carboxyphenyl pentopyranosylamines, N-p-methylphenyl-1-deoxy-D-fructosylamine (the Amadori compound) and N-3-ethylindole-D-xylopyranosylamine were shown to be direct-acting mutagens in Salmonella typhimurium TA100. The activity of some of the compounds was similar to that of N-ethyl-N-nitrosourea. Their mutagenic activity was shown to depend on the structure of the amine and the sugar moieties and to require the presence of free hydroxyl groups in the sugar. The mutagenicity of N-nitrosoglycosylamines was attributed to their hydrolysis to arenediazonium cations. The formation of these compounds was detected by azo-coupling with N-ethyl-1-naphthylamine, using spectrophotometric and mass spectrometric analyses. These data implicate arene(alkyl)diazonium cations as the ultimate mutagens of N-nitrosoglycosylamines (and possibly of N-nitroso Amadori compounds), a little-explored class of N-nitroso compounds that may be formed in vivo.

Synthesis, antitumor activity, distribution and toxicity of 4-[4-[bis(2-chloroethyl)amino]phenyl]-1-hydroxybutane-1 1-bisphosphonic acid (BAD), a new lost derivative with increased accumulation in rat osteosarcoma

The aim of this study was to investigate whether the newly synthesized bisphosphonic acid-linked N-Lost derivative BAD retains bone-seeking and cytostatic properties. The paper describes experiments on mutagenicity in vitro and on toxicity in vivo. BAD is characterized by very low mutagenic activity toward histidine auxotrophic Salmonella typhimurium strains. Cytotoxic effects were tested in rat osteosarcoma and in Walker carcinosarcoma 256B. The LD50 of i.v. injected BAD was 146 mg/kg. Acute toxicity is probably caused by calcium complexing of the bisphosphonate part of the molecule. Labeling experiments showed moderate accumulation in bone and osteosarcoma, as well as in lung metastases. BAD effected high tumor growth inhibition in osteosarcoma and Walker carcinosarcoma-bearing rats and marked prolongation of survival; histologic and radiographic examination revealed rapid calcification of osteosarcoma and lung metastases. BAD-pretreatment produced protective effects against osteolysis induced by intratibially implanted Walker carcinosarcoma ascites cells. The cytostatic efficacy of equitoxic doses of BAD in rat osteosarcoma is comparable to that of dacarbazine and in Walker carcinosarcoma to that of melphalan.