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Production of frameshift mutations in Salmonella by phenanthridinium derivatives: enzymatic activation and
Abstract:
The effect of metabolic activation on the mutagenic potential of some phenanthridinium compounds was examined in Salmonella typhimurium strains TA1538 and TA1978 . All of the compounds tested were mutagenic in TA1538, a DNA excision-repair-deficient strain, when metabolizing enzymes were included in the assay. Reversions were not detected when these compounds were examined under the same conditions in TA1978 , the isogenic strain of TA1538 proficient in DNA repair. The mutagenic activity of an azido analog of propidium iodide was also examined using photoactivation and enzymatic activation, and with both conditions, reversions were observed in TA1538 but not in TA1978 . Furthermore, the ranking of mutagenic activity of propidium azide relative to ethidium azide analogs was comparable for both types of activation. The evidence from several studies suggests that the structural requirements for mutagenic activity for this series of phenanthridinium compounds appear to be the same whether mutagenesis is induced via photoactivation or metabolic activation. The interaction with DNA resulting in covalent alteration of the DNA is implicated as the mutagenic mechanism whether the active species is generated by metabolic- or photo-activation.
Insights
Metabolic activation enhances the mutagenic potential of phenanthridinium compounds in DNA repair-deficient bacteria. These compounds cause DNA alterations, indicating a consistent mutagenic mechanism across different activation methods.
Area of Science:
- Toxicology
- Molecular Biology
- Genetics
Background:
- Phenanthridinium compounds are known for their biological activity.
- Understanding their mutagenic potential is crucial for safety assessment.
- Metabolic activation can alter the toxicity of chemical compounds.
Purpose of the Study:
- To investigate the mutagenic effects of phenanthridinium compounds after metabolic activation.
- To compare mutagenicity in bacterial strains with different DNA repair capacities.
- To explore the role of DNA interaction in phenanthridinium-induced mutagenesis.
Main Methods:
- Bacterial mutagenicity assays using Salmonella typhimurium strains TA1538 (DNA repair-deficient) and TA1978 (DNA repair-proficient).
- Inclusion of metabolizing enzymes to assess metabolic activation.
- Photoactivation and enzymatic activation were used to study an azido analog of propidium iodide.
- Comparison of mutagenic activity rankings across different activation methods.
Main Results:
- All tested phenanthridinium compounds were mutagenic in TA1538 strains with metabolic activation.
- No mutagenic activity was observed in the DNA repair-proficient TA1978 strain under the same conditions.
- Mutagenic activity of propidium iodide analog was observed in TA1538 but not TA1978, regardless of activation method (photo- or enzymatic).
- The ranking of mutagenic activity was consistent between photoactivation and metabolic activation.
Conclusions:
- Metabolic activation significantly influences the mutagenic potential of phenanthridinium compounds.
- DNA repair proficiency in bacteria like Salmonella typhimurium TA1978 can prevent mutagenesis.
- The mutagenic mechanism likely involves direct DNA interaction and covalent alteration, irrespective of the activation pathway (metabolic or photoactivation).