Some studies on the DNA-repair-eliciting and genotoxic activity of cell-free extracts of Lactobacillus bifidus

Abstract

Cell-free extracts of Lactobacillus bifidus have been reported as possessing DNA-repair-eliciting properties in UV-irradiated human cells, and suggestions have been made that these extracts could be used to protect human skin cells from DNA-damaging effects induced by natural UV light. In view of the importance of these findings, and because extracts of other bifidobacteriae had previously been shown to possess genotoxic activity in bacterial systems, it seemed appropriate to perform some experiments aimed at evaluating the ability of cell-free extracts of L. bifidus, as well as the bacterial suspension medium, to modulate DNA repair and/or to exert potentially adverse genotoxic effects in a variety of mammalian cells in culture. Chinese hamster cells, human fibroblasts, and human lymphocytes were used to evaluate the influence of the extract on the repair of UV-damaged DNA and on several biological effect (cell cycle progression, cell killing, chromosomal aberrations, and sister-chromatid exchanges) induced by DNA-damaging agents. The results show that neither the extract nor the suspension have any influence on DNA repair or other biological endpoints induced by UV and other DNA-damaging agents. In conclusion, the present findings do not indicate that cell-free extracts of L. bifidus specifically promote the repair of UV-damaged DNA in human cells. Neither do they indicate that these extracts have a promoting activity on UV-induced (misrepair) mutagenesis in mammalian cells. Finally, the present experiments indicate that the L. bifidus extracts used in our experiments are devoid of any direct mutagenic and/or genotoxic activity in mammalian cells. © 1988.