Enhancement of Ultraviolet B-Induced Apoptosis and Elimination of DNA Damage by Pre-Irradiation with Infrared Radiation A Does Not Depend on DNA Damage Repair.

Abstract

We previously reported that pre-irradiation with infrared radiation A (IRA) eliminated ultraviolet B (UVB) -induced cyclobutane pyrimidine dimers (CPDs). Accelerated elimination of CPDs could have resulted from enhanced DNA repair and/or enhanced induction of apoptosis. Using Xpa knockout (KO) mice, which are deficient in DNA repair, we examined whether IRA accelerated elimination of CPDs by enhancing DNA repair. We have already generated mice harboring epidermal melanocytes that produce only eumelanin and dominant pheomelanin, and no melanin. To obtain such mice with impaired DNA repair ability, we backcrossed them with Xpa KO mice. Three hours before UVB irradiation, the mice were irradiated with IRA, and CPDs and apoptotic cells were examined. Pre-irradiation of Xpa KO mice with IRA before UVB irradiation accelerated removal of CPDs and enhanced apoptotic changes. These results indicate that enhancement of UVB-induced apoptosis and acceleration of removal of CPDs by pre-irradiation with IRA does not depend on DNA damage repair.