Effects of Black Raspberry Extract and Berry Compounds on Repair of DNA Damage and Mutagenesis Induced by Chemical and Physical Agents in Human Oral Leukoplakia and Rat Oral Fibroblasts

Black raspberries (BRB) have been shown to inhibit carcinogenesis in a number of systems, with most studies focusing on progression. Previously we reported that an anthocyanin-enriched black raspberry extract (BE) enhanced repair of dibenzo-[<i>a,l</i>]-pyrene dihydrodiol (DBP-diol)-induced DNA adducts and inhibited DBP-diol and DBP-diolepoxide (DBPDE)-induced mutagenesis in a <i>lacI</i> rat oral fibroblast cell line, suggesting a role for BRB in the inhibition of initiation of carcinogenesis. Here we extend this work to protection by BE against DNA adduct formation induced by dibenzo-[<i>a,l</i>]-pyrene (DBP) in a human oral leukoplakia cell line (MSK) and to a second carcinogen, UV light. Treatment of MSK cells with DBP and DBPDE led to a dose-dependent increase in DBP-DNA adducts. Treatment of MSK cells with BE after addition of DBP reduced levels of adducts relative to cells treated with DBP alone, and treatment of rat oral fibroblasts with BE after addition of DBPDE inhibited mutagenesis. These observations showed that BE affected repair of DNA adducts and not metabolism of DBP. As a proof of principle we also tested aglycones of two anthocyanins commonly found in berries, delphinidin chloride and pelargonidin chloride. Delphinidin chloride reduced DBP-DNA adduct levels in MSK cells, while PGA did not. These results suggested that certain anthocyanins can enhance repair of bulky DNA adducts. As DBP and its metabolites induced formation of bulky DNA adducts, we investigated the effects of BE on genotoxic effects of a second carcinogen that induces bulky DNA damage, UV light. UV irradiation produced a dose-dependent increase in cyclobutanepyrimidine dimer levels in MSK cells, and post-UV treatment with BE resulted in lower cyclobutanepyrimidine dimer levels. Post-UV treatment of the rat <i>lacI</i> cells with BE reduced UV-induced mutagenesis. Taken together, the results demonstrate that BE extract reduces bulky DNA damage and mutagenesis and support a role for BRB in the inhibition of initiation of carcinogenesis

Mechanisms Underlying the Varied Mammary Carcinogenicity of the Environmental Pollutant 6‑Nitrochrysene and Its Metabolites (−)‑[<i>R</i>,<i>R</i>]- and (+)‑[<i>S</i>,<i>S</i>]‑1,2-Dihydroxy-1,2-dihydro-6-nitrochrysene in the Rat

The mechanisms that can account for the remarkable mammary carcinogenicity of the environmental pollutant 6-nitrochrysene (6-NC) in the rat remain elusive. In our previous studies, we identified several 6-NC-derived DNA adducts in the rat mammary gland; one major adduct was derived from (±)-<i>trans</i>-1,2-dihydroxy-1,2-dihydro-6-nitrochrysene (1,2-DHD-6-NC). In the present study, we resolved the racemic (±)-1,2-DHD-6-NC into (−)-[<i>R</i>,<i>R</i>]- and (+)-[<i>S</i>,<i>S</i>]-1,2-DHD-6-NC and compared their <i>in vivo</i> mutagenicity and carcinogenicity in the mammary glands of female transgenic (BigBlue F344 × Sprague–Dawley)­F1 rats harboring <i>lacI</i>/<i>cII</i> and Sprague–Dawley rats, respectively. Both [<i>R</i>,<i>R</i>]- and [<i>S</i>,<i>S</i>]-isomers exerted similar mutagenicity and carcinogenicity but were less potent than 6-NC. Additional <i>in vivo</i> and <i>in vitro</i> studies were then performed to explore possible mechanisms that can explain the higher potency of 6-NC than 1,2-DHD-6-NC. Using ELISA, we found that neither 6-NC nor 1,2-DHD-6-NC increased the levels of several inflammatory cytokines in plasma obtained from rats 24 h after treatment. In MCF-7 cells, as determined by immunoblotting, the effects of 6-NC and 1,2-DHD-6-NC on protein expression (p53, Akt, p38, JNK, c-myc, bcl-2, PCNA, and ERβ) were comparable; however, the expressions of AhR and ERα proteins were decreased by 6-NC but not 1,2-DHD-6-NC. The expression of both receptors was decreased in mammary tissues of rats treated with 6-NC. Our findings suggest that the differential effects of 6-NC and 1,2-DHD-6-NC on AhR and ERα could potentially account for the higher carcinogenicity of 6-NC in the rat mammary gland