Normal Human Keratinocytes Pretreated with Damaged mRNA Are Resistant to UVB Damage and Exhibit Increased DNA Repair

Abstract

Treatment of normal human keratinocytes with UVC-irradiated rabbit globin mRNA 24 h before and after UVB exposure increased the survival of the human keratinocytes. We also observed that UVC-damaged mRNA reduced the formation of sunburn cells in skin models. We next tested the effects of UVC-damaged mRNA on cellular repair of DNA. DNA repair was evaluated using 2 assay methods. The first method used a damaged plasmid that is transfected back into the cell where it is repaired by the host cell repair mechanism. In these experiments, we observed that externally added UVC-damaged rabbit globin mRNA enhanced the repair of a plasmid transfected into the host keratinocyte cells. The second method used to determine the effects on DNA repair was direct immunostaining for thymidine-thymidine dimers (TT dimers) in histological sections of the skin models. Skin models were irradiated with UVB and then fixed immediately or after 24 h and stained for TT dimers. UVB irradiation immediately caused an increase in the number of stained keratinocytes in the skin. The number of stained cells decreased in skin fixed 24 h after UVB. This is due to repair of the TT dimers and their removal. Sections of skin models pretreated with UV-damaged mRNA exhibit greater removal of these TT dimers after 24 h. The above evidence suggests that damaged mRNA can trigger a host cell DNA repair pathway.

UV Protective Effects of DNA Repair Enzymes and RNA Lotion

“…They have likewise been shown to prevent UV‐induced upregulation of immunosuppressive cytokines such as IL‐10 and TNF‐α in human skin (16). Published reports on the in vivo use of RNA fragments for photoprotection do not exist, although in vitro data suggest an increased survival of keratinocytes, decreased sunburn cell formation and DNA damage (17).…”

“…We aimed to determine the effects of two topical formulations containing (1) DNA repair enzymes ( Micrococcus luteus ) (18–20), or (2) fragments of UVC‐irradiated rabbit globin mRNA (17,21), on UV‐induced contact hypersensitivity (CHS) suppression in human subjects. A corollary aim was to measure the effects of these agents on levels of thymine dimers in skin biopsies obtained after simulated solar radiation (SSR).…”