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beta-Carotene reduces bleomycin-induced genetic damage in human lymphocytes
Michael Glei1, Ute Monika Liegibel, Miriam Nannette Ebert
1Institute for Nutrition, Friedrich Schiller University, Dornburger Str. 25, Jena, D-07743, Germany.
Abstract:
We had previously shown in a human feeding study that ingestion of tomato and carrot juices decreases DNA breaks and oxidized pyrimidine bases in peripheral lymphocytes and enhances expression of glutathione S-transferase (GST) in a subpopulation of the volunteers. The aim of this study was to determine how the major carotenoids of these juices (beta-carotene or lycopene) could contribute to the observed antigenotoxicity. Physiological concentrations (2 microM) of water-soluble beta-carotene and lycopene were incubated for 18-24 h with lymphocytes and then treated with bleomycin or H(2)O(2). Strand breaks, oxidized DNA bases, and persistence of damage (DNA repair) were measured by single-cell microgelelectrophoresis. GST-protein (GSTP1) was determined using an immunoassay and by measuring enzyme activity. HPLC analysis showed that beta-carotene was taken up by the cells after 24 h, and this was associated with a reduction of bleomycin-induced damage (29.11 +/- 1.86% tail intensity without versus 21.54 +/- 2.36% with beta-carotene). Lycopene was ineffective. The carotenoids did not modulate repair of bleomycin- and H(2)O(2)-induced damage and did not alter levels of oxidized pyrimidine bases nor GST expression. The results indicate that beta-carotene can enter the cell and protect against strand breaks but not against oxidized DNA bases. Therefore, beta-carotene accounts for only part of the protection observed in vivo with carotenoid-rich vegetable juices.
Insights
Beta-carotene from vegetable juices protects lymphocytes from DNA strand breaks, but not oxidized bases. Lycopene showed no protective effect, indicating beta-carotene contributes partially to the antigenotoxicity of these juices.
Area of Science:
- Nutrition Science
- Molecular Biology
- Toxicology
Background:
- Previous human studies demonstrated that tomato and carrot juice consumption reduces DNA damage and enhances glutathione S-transferase (GST) expression.
- The specific carotenoids responsible for these protective effects in vegetable juices were not identified.
Purpose of the Study:
- To investigate the individual contributions of beta-carotene and lycopene to the antigenotoxic effects observed with tomato and carrot juices.
- To determine if beta-carotene or lycopene protect lymphocytes against DNA damage and modulate GST expression.
Main Methods:
- Human lymphocytes were incubated with physiological concentrations of beta-carotene or lycopene.
- Cells were subsequently exposed to bleomycin or hydrogen peroxide (H2O2) to induce DNA damage.
- DNA strand breaks, oxidized DNA bases, DNA repair, and GSTP1 levels were assessed using single-cell microgelelectrophoresis, immunoassay, and enzyme activity measurements.
Main Results:
- Beta-carotene was taken up by lymphocytes and significantly reduced bleomycin-induced DNA strand breaks.
- Lycopene did not demonstrate any protective effect against DNA damage.
- Neither carotenoid influenced DNA repair, oxidized base levels, or GST expression.
Conclusions:
- Beta-carotene exhibits protective effects against DNA strand breaks in lymphocytes, but not against oxidized DNA bases.
- The antigenotoxicity of carotenoid-rich vegetable juices is only partially explained by beta-carotene's action.
- Further research is needed to identify other components contributing to the observed health benefits of these juices.