Treatment of Human HeLa Cells with Black Raspberry Extracts Enhances the Removal of DNA Lesions by the Nucleotide Excision Repair Mechanism

As demonstrated by us earlier and by other researchers, a diet containing freeze-dried black raspberries (BRB) inhibits DNA damage and carcinogenesis in animal models. We tested the hypothesis that the inhibition of DNA damage by BRB is due, in part, to the enhancement of DNA repair capacity evaluated in the human HeLa cell extract system, an established in vitro system for the assessment of cellular DNA repair activity. The pre-treatment of intact HeLa cells with BRB extracts (BRBE) enhances the nucleotide excision repair (NER) of a bulky deoxyguanosine adduct derived from the polycyclic aromatic carcinogen benzo[a]pyrene (BP-dG) by similar to 24%. The NER activity of an oxidatively-derived non-bulky DNA lesion, guanidinohydantoin (Gh), is also enhanced by similar to 24%, while its base excision repair activity is enhanced by only similar to 6%. Western Blot experiments indicate that the expression of selected, NER factors is also increased by BRBE treatment by similar to 73% (XPA), similar to 55% (XPB), while its effects on XPD was modest (<14%). These results demonstrate that BRBE significantly enhances the NER yields of a bulky and a non-bulky DNA lesion, and that this effect is correlated with an enhancement of expression of the critically important NER factor XPA and the helicase XPB, but not the helicase XPD.

Automated summary

The study demonstrates that the consumption of a diet containing freeze-dried black raspberries (BRB) can inhibit DNA damage and carcinogenesis. The researchers tested the effects of BRB extracts (BRBE) on DNA repair capacity using the HeLa cell extract system and found that BRBE enhances nucleotide excision repair (NER) activity and increases the expression of important NER factors. These findings suggest that BRBE can improve the repair of bulky and non-bulky DNA lesions.