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Suppressive effects of urine on the SOS responses induced by UV and chemical mutagens
S Ikemoto1, M Kamizuru, N Hayahara
1Department of Urology, Osaka City University Medical School, Japan.
Abstract:
We studied the antimutagenic effects of urine on the SOS-inducing activity of mutagenic substances by using a novel test system (umu-test) for detecting DNA damaging agents, which uses a new tester strain (Salmonella typhimurium TA1535/pSK1002). The SOS-inducing activity of chemicals was detected in terms of the level of umu operon expression by measuring beta-galactosidase activity. We first examined the effects of various amounts of urine on SOS responses caused by mitomycin C (MMC). As a result, the urine suppressed beta-galactosidase activity of MMC dose-dependently. A urine concentration of 50 microliters/ml in the medium also suppressed 89.9% of SOS response induced by 0.1 microgram/ml of PEP, 75.6% of that induced by 0.02 microgram/ml of AF2 and 60.9% of that induced by 0.1 microgram/ml of AFB1. In addition, a urine concentration of 50 microliters/ml in the medium also suppressed 85.6% of SOS response by 5 J/m2 of UV irradiation. The observed suppression seemed to be directly related to the SOS responses at a cellular level, rather than to interaction between urine and mutagens, because the urine suppressed SOS responses induced not only by various mutagens but also by UV irradiation. These results suggest that urine works as a strong antimutagen against UV and chemical substances.
Insights
Urine demonstrates significant antimutagenic properties, effectively suppressing DNA damage responses caused by various mutagens and UV radiation. This study highlights urine
Area of Science:
- Biochemistry
- Genetics
- Toxicology
Background:
- Mutagenic substances pose risks to DNA integrity.
- The SOS response is a cellular defense mechanism against DNA damage.
- Antimutagenic compounds can protect against mutagenicity.
Purpose of the Study:
- To investigate the antimutagenic effects of human urine.
- To evaluate urine's ability to inhibit the SOS-inducing activity of mutagens.
- To assess urine's protective role against DNA damage.
Main Methods:
- Utilized a novel umu-test system with Salmonella typhimurium TA1535/pSK1002.
- Measured beta-galactosidase activity to detect umu operon expression (SOS response).
- Assessed the dose-dependent effects of urine on SOS responses induced by mitomycin C, PEP, AF2, AFB1, and UV irradiation.
Main Results:
- Urine significantly suppressed beta-galactosidase activity in a dose-dependent manner.
- A urine concentration of 50 µl/ml inhibited SOS responses induced by various chemical mutagens (PEP, AF2, AFB1) and UV irradiation.
- Suppression of SOS responses was observed directly at the cellular level, independent of direct mutagen-urine interaction.
Conclusions:
- Human urine exhibits strong antimutagenic activity against both chemical mutagens and UV radiation.
- Urine's protective effects are mediated at the cellular level by suppressing SOS responses.
- These findings suggest urine possesses protective properties against DNA-damaging agents.