Cyclo(phenylalanine-proline) induces DNA damage in mammalian cells via reactive oxygen species

Cyclo(phenylalanine-proline) is produced by various organisms such as animals, plants, bacteria and fungi. It has diverse biological functions including anti-fungal activity, anti-bacterial activity and molecular signalling. However, a few studies have demonstrated the effect of cyclo(phenylalanine-proline) on the mammalian cellular processes, such as cell growth and apoptosis. In this study, we investigated whether cyclo(phenylalanine-proline) affects cellular responses associated with DNA damage in mammalian cells. We found that treatment of 1 mM cyclo(phenylalanine-proline) induces phosphorylation of H2AX (S139) through ATM-CHK2 activation as well as DNA double strand breaks. Gene expression analysis revealed that a subset of genes related to regulation of reactive oxygen species (ROS) scavenging and production is suppressed by the cyclo(phenylalanine-proline) treatment. We also found that cyclo(phenylalanine-proline) treatment induces perturbation of the mitochondrial membrane, resulting in increased ROS, especially superoxide, production. Collectively, our study suggests that cyclo(phenylalanine-proline) treatment induces DNA damage via elevation of ROS in mammalian cells. Our findings may help explain the mechanism underlying the bacterial infection-induced activation of DNA damage response in host mammalian cells.