Abstract
The hormone 17ß-estradiol (E2) causes oxidative DNA damage via redox cycling of its metabolites such as 4-hydroxy estradiol (4E2). In this study, ACI rats (8 wk old) were fed either AIN-93M diet or diets supplemented with 0.5% each of mixed berries (strawberry, blueberry, blackberry, and red and black raspberry), blueberry alone (BB; 2.5%), or ellagic acid (EA; 400 ppm) from 2 wk prior to and up to 12 wk of E2 treatment. The liver DNA was analyzed for the presence of 8-oxo-7,8-dihydroguanine (8-oxodG) and other polar adducts by 32P-postlabeling. Compared to sham treatment, E2 significantly increased the levels of both 8-oxodG and P-1 subgroup (259% and 214%, respectively; P< 0.05). EA diet significantly reduced E2-induced levels of 8-oxodG, P-1, P-2, and PL-1 by 79, 63, 44, and 67%, respectively (P< 0.001). BB diet also significantly reduced the levels of P-1, P-2, and PL-1 subgroups by 77, 43, and 68%, respectively (P< 0.001). Mixed berries were, however, ineffective. In addition, aqueous extracts of berries (2%) and EA (100 μM) were tested for their efficacy in diminishing oxidative DNA adducts induced by redox cycling of 4E2 catalyzed by copper chloride in vitro. EA was the most efficacious (90%), followed by extracts of red raspberry (70%), blueberry, and strawberry (50% each; P< 0.001).
ACKNOWLEDGMENTS
The authors would like to thank Drs. Manicka Vadhanam and Srivani Ravoori for their help with the ACI rat implants. Contributions of Isabelle Jean, a visiting summer student from Dijon, France, in preparing the berry extracts is gratefully acknowledged. This work was supported by grants from U.S. Public Health Service CA-90892 and CA-114118. H. S. Aiyer was supported, in part, by a Graduate School Fellowship from the University of Kentucky, Lexington, Kentucky. Part of the work was conducted at the authors' previous affiliation: Department of Preventive Medicine and Environmental Health and The Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky.
Notes
a Calculated from ellagic acid contents described in Daniel et al. (Citation29).
b Anthocyanin contents described in Wu et al. (Citation30).
a Adducts were separated by 2-directional polyethyleneimine thin-layer chromatography using solvent composition as described in Materials and Methods and visualized using a Packard InstantImager®. Each subgroup of adduct was individually measured and quantified using the formula relative adduct labeling = counts per minute (cpm) adducts/cpm normal nucleotides × 1/dilution factor as described (Citation26). The values represented are the mean of 3 separate analyses. All groups were compared to E2 + control diet using 1-way analysis of variance followed by a Tukey's post hoc test.