Possible benefits of tomato juice consumption: a pilot study on irradiated human lymphocytes from healthy donors

Abstract

Background: Reactive oxygen species (ROS) mediate much of the DNA damage caused by ionizing radiation. Among carotenoids, lycopene and β-carotene, present in tomato juice, are known to be strong radical scavengers. The aim of the study was to investigate the effect of tomato juice intake on the levels of DNA damage and oxidative stress in human whole blood induced by in vitro exposure to X-rays.

Methods: Ten healthy adults were asked to drink 190 g of tomato juice, containing 17 mg lycopene and 0.25 mg β-carotene, per day for 3 weeks and then refrain from drinking it for 3 weeks. Peripheral whole blood samples were collected before and after the intake period of tomato juice and after the washout period. The blood samples were exposed in vitro to X-ray doses of 0, 0.1, 0.5, and 2 Gy. Cytogenetic damage was measured using the cytokinesis-block micronucleus (CBMN) assay and the dicentrics (DIC) assay. The level of oxidative stress was determined using serum 8-oxo-7, 8-dihydro-2-deoxyguanosine (8-oxo-dG) and plasma reactive oxygen metabolite-derived compounds (d-ROMs). The concentration of carotenoids in plasma was measured at the three time points.

Results: The levels of 8-oxo-dG tended to decrease during the intake period and increase during the washout period. A non-significant inverse correlation was noted between the plasma concentration of lycopene plus β-carotene and the level of 8-oxo-dG (P = 0.064). The radiation-induced MN and DIC frequencies increased in a dose-dependent manner, and when compared at the same dose, the MN and DIC frequencies decreased during the intake period compared with those at baseline and then increased during the washout period. The results suggest that continuous tomato juice consumption non-significantly decreases extracellular 8-oxo-dG, d-ROMs, and MN. Tomato juice intake had minimal or no effect on radiation-induced 8-oxo-dG and d-ROMs. For most radiation doses, continuously tomato juice intake lowered the levels of MN and DIC.

Conclusion: Tomato juice consumption may suppress human lymphocyte DNA damage caused by radiation, but further examination is required.

Trial registration: 2014-001 and 2014-R06.

Keywords: Human lymphocytes; Lycopene; Radioprotective effect; Reactive oxygen species; Tomato juice; β-carotene.

Fig. 1

Radiation effects on the level of main carotenoids in human blood. a Concentration of lycopene according to radiation dose at each time point. Values are given as mean ± SE of 10 donors. b Structure ratio of lycopene (cis/trans) according to radiation dose. The ratio was constant between the different radiation doses. c Concentration of β-carotene according to radiation dose at each time point. Values are given as mean ± SE of 10 donors. a: different from baseline P < 0.05, b: different from washout P < 0.05 by Bonferroni/Dunn test. Concentrations of carotenoids after each period did not differ significantly by radiation (1a, 1c)

Fig. 2

The level of oxidative stress-related markers in human blood. a Level of 8-oxo-dG in serum. b Level of d-ROMs in plasma. Values are given as mean ± SE of 10 donors. *P < 0.05, #: different between base line and intake period P = 0.059, $: different between base line and washout period P = 0.092 by (a) Wilcoxon signed-ranks test and (b) paired t test

Fig. 3

Relationship between concentration of lycopene plus β-carotene and level of 8-oxo-dG in serum in the non-irradiated samples. The P value was determined by linear regression analysis

Fig. 4

Changes in the level of MN in human lymphocytes. Values are given as mean ± SE of 10 donors. *P < 0.05 by paired t test. a 0 Gy. b 0.1 Gy. c 0.5 Gy. d 2 Gy

Fig. 5

Changes in the level of DIC in human lymphocytes. Values are given as mean ± SE of 10 donors. *P < 0.05 by paired t test. a 0 Gy. b 0.1 Gy. c 0.5 Gy. d 2 Gy