Combined metformin and resveratrol confers protection against UVC-induced DNA damage in A549 lung cancer cells via modulation of cell cycle checkpoints and DNA repair.

Aging in humans is a multi-factorial cellular process that is associated with an increase in the risk of numerous diseases including diabetes, coronary heart disease and cancer. Aging is linked to DNA damage, and a persistent source of DNA damage is exposure to ultraviolet (UV) radiation. As such, identifying agents that confer protection against DNA damage is an approach that could reduce the public health burden of age-related disorders. Metformin and resveratrol have both shown effectiveness in preventing several age-related diseases; using human A549 cells, we investigated whether metformin or resveratrol, alone or combined, prevent UVC-induced DNA damage. We found that metformin inhibited UVC-induced upregulation of p53, as well as downregulated the expression of two DNA damage markers: γH2AX and p-chk2. Metformin also upregulated DNA repair as evidenced by the increase in expression of p53R2. Treatment with metformin also induced cell cycle arrest in UVC-induced cells, in correlation with a reduction in the levels of cyclin E/cdk2/Rb and cyclin B1/cdk1. Compared to metformin, resveratrol as a single agent showed less effectiveness in counteracting UVC-elicited cellular responses. However, resveratrol displayed synergism when combined with metformin as shown by the downregulation of p53/γH2AX/p-chk2. In conclusion, the results of the present study validate the effectiveness of metformin, alone or with the addition of resveratrol, in reducing the risk of aging by conferring protection against UV-induced DNA damage.