PREVENTION OF OXIDATIVE DNA-DAMAGE IN RATS BY BRUSSELS-SPROUTS

The alleged cancer preventive effects of cruciferous vegetables could be related to protection from mutagenic oxidative DNA damage. We have studied the effects of Brussels sprouts, some non-cruciferous vegetabl es and isolated glucosinolates on spontaneous and induced oxidative DN A damage in terms of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in groups of 6-8 male Wistar rats. Excess oxidative DNA damage was induce d by 2-nitropropane (2-NP 100 mg/kg). Four days oral administration of 3 g of cooked Brussels sprouts homogenate reduced the spontaneous uri nary 8-oxodG excretion by 31% (p<0.05) whereas raw sprouts, beans and endive (1 : 1), isolated indolyl glucosinolates and breakdown products had no significant effect. An aqueous extract of cooked Brussels spro uts (corresponding to 6.7 g vegetable per day for 4 days) decreased th e spontaneous 8-oxodG excretion from 92 +/- 12 to 52 +/- 15 pmol/24 h (p < 0.05). After 2-NP administration the 8-oxodG excretion was increa sed to 132+/-26 pmol/24 h (p<0.05) whereas pretreatment with the sprou ts extract reduced this to 102 +/- 30 pmol/24 h (p < 0.05). The sponta neous level of 8-oxodG in nuclear DNA from liver and bone marrow was n ot significantly affected by the sprouts extract whereas the level dec reased by 27% in the kidney (p < 0.05). In the liver 2-NP increased th e 8-oxodG levels in nuclear DNA 8.7 and 3.8 times (p<0.05) 6 and 24 h after dose, respectively. The sprouts extract reduced this increase by 57% (p<0.05) at 6 h whereas there was no significant effect at 24 h. In the kidneys 2-NP increased the 8-oxodG levels 2.2 and 1.2 times (p < 0.05) 6 and 24 h after dose, respectively. Pretreatment with the spr outs extract abolished these increases (p<0.05). Similarly, in the bon e marrow the extract protected completely (p < 0.05) against a 4.9-fol d 2-NP induced increase (p < 0.05) in the 8-oxodG level. These finding s demonstrate that cooked Brussels sprouts contain bioactive substance (s) with a potential for reducing the physiological as well as oxidati ve stress induced oxidative DNA damage in rats. This could explain the suggested cancer preventive effect of cruciferous vegetables. The cor respondence between the urinary excretion and 8-oxodG levels in 2-NP t arget organs supports its being the main repair product that reflects the rate of guanine oxidation in DNA.