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

Biological Effects of Maillard Browning Products That May Affect Acrylamide Safety in Food

The heat-induced reaction of amino groups of amino acids, peptides, and proteins with carbonyl groups of reducing sugars such as glucose results in the concurrent formation of so-called Maillard browning products and acrylamide. For this reason, reported studies of adverse biological effects of pure acrylamide may not always be directly relevant to acrylamide in processed food, which may contain Maillard and other biologically active products. These may either antagonize or potentiate the toxicity of acrylamide. To stimulate progress, this paper presents an overview of selected reported studies on the antiallergenic/allergenic, antibiotic, anticarcinogenic/carcinogenic antimutagenic/mutagenic, antioxidative/oxidative, clastogenic (chromosome-damaging), and cytotoxic activities of Maillard products, which may adversely or beneficially impact the toxicity of acrylamide. The evaluation of biological activities of Maillard products and of other biologically active food ingredients suggests that they could both enhance and/or ameliorate acrylamide toxicity, especially carcinogenicity, but less so neurological or reproductive manifestations. Future studies should be directed to differentiate the individual and combined toxicological relationships among acrylamide and the Maillard products, define individual and combined potencies, and develop means to prevent the formation of both acrylamide and the most toxic Maillard products. Such studies should lead to safer foods.

The tumor promoting effect of lime-piper betel quid in JB6 cells

Betel quid chewing is a general behavior in Taiwan, India, southeastern Asian and South Africa. In this study, microculture tetrazolium test (MTT) showed that the extract of lime-piper betel quid (LPB) (1.0-20 mg/ml) was toxic to JB6 cells. Cells exposed of LPB (0.1, 0.5, 1.0 mg/ml) for 7 days resulted in changes in cytomorphology with characteristics of carcinogenesis. With a long-term treatment (approximately 30 days) of low doses of LPB (1, 5, 10 microg/ml), the production of H2O2 and the activity of myeloperoxidase (MPO) and ornithine decarboxylase (ODC) were increased in JB6 cells. Cell cycle analysis showed a decrease in the G1 phase and an accumulation in the S phase 48 h after LPB treatment. When treating with 0.5 mg/ml LPB for 15 days as a promoter, type III foci were formed in the JB6 culture. These results demonstrated the tumor promotional effect of LPB in JB6 cells.

Use of a cell transformation assay with established cell lines, and a metabolic cooperation assay with V79 cells for the detection of tumour promoters: a review

Extensive studies on the safety evaluation of chemicals have indicated that a considerable number of non-genotoxic chemicals are carcinogenic. Tumour promoters are likely to be among these non-genotoxic carcinogens, and their detection is considered to be an important approach to the prevention of cancer. In this review, the results are summarised for in vitro transformation assays involving established cell lines, and for an assay for inhibition of gap junctional intercellular communication for the detection of tumour promoters, which involves V79 cells. Although the number of chemicals examined is still too small to permit a full evaluation of the correlation between in vitro cell transformation and in vivo carcinogenicity, it is clear that the sensitivity of the focus formation assay is very high. In the case of the metabolic cooperation assay, the sensitivity appears to be rather poor, but the assay can be considered to be useful because of its simple procedure and its considerable database. These in vitro assays for tumour promoters are recommended as useful tools for the detection of non-genotoxic carcinogens.

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.