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Formation of bacterial mutagens from the reaction of chewing tobacco with nitrite
Abstract:
Using the Salmonella/microsome assay system, the mutagenicity of chewing tobacco extracts (CTE) treated with and without sodium nitrite under acidic conditions was examined. Mutagenic activity was found only for nitrite-treated CTE in both tester strains, TA98 and TA100, and was independent of metabolic activation. Formation of mutagenic substances from CTE by nitrite was dependent on acidic pHs (the highest at pH 2) and could be inhibited by ascorbate. The mutagenic potency of CTE plus nitrite was proportional to the content of nitroso compounds generated in the reaction mixture, indicating that the nitrosation process was involved. The possible in vivo nitrosation and the potential health effect are discussed.
Insights
Chewing tobacco extracts treated with sodium nitrite under acidic conditions are mutagenic, forming cancer-causing nitroso compounds. This mutagenicity, observed in the Salmonella/microsome assay, can be inhibited by ascorbate.
Area of Science:
- Toxicology
- Chemical carcinogenesis
- Food safety
Background:
- Chewing tobacco is a significant source of exposure to tobacco-specific nitrosamines.
- The mutagenicity of chewing tobacco extracts (CTE) and the role of sodium nitrite in its formation are not fully understood.
Purpose of the Study:
- To investigate the mutagenicity of CTE treated with sodium nitrite under acidic conditions.
- To identify the chemical processes involved in the formation of mutagenic substances.
Main Methods:
- Salmonella/microsome assay (Ames test) using tester strains TA98 and TA100.
- Treatment of CTE with sodium nitrite at various acidic pH levels.
- Quantification of nitroso compounds and assessment of ascorbate inhibition.
Main Results:
- Nitrite-treated CTE exhibited mutagenic activity in both tester strains, independent of metabolic activation.
- Mutagen formation was pH-dependent, with optimal activity at pH 2.
- Ascorbate significantly inhibited the formation of mutagenic substances.
- Mutagenic potency correlated with the concentration of generated nitroso compounds, implicating nitrosation.
Conclusions:
- Sodium nitrite can induce mutagenicity in chewing tobacco extracts under acidic conditions via nitrosation.
- The formation of these mutagenic nitroso compounds raises concerns about potential in vivo nitrosation and health risks associated with chewing tobacco consumption.