Enhancement of UVB-induced apoptosis and elimination of DNA damages by irradiation of IPL does not depend on the repair of DNA damages

Abstract

We have previously reported that repetitive irradiation of Intense Pulsed Light (IPL, 580–1200 nm) on hairless mice which harbor epidermal melanocytes producing only eumelanin (BHSCF mice) or pheomelanin (YHSCF mice), as well as no melanin (WHSCF mice) by back-crossing the K14-SCF mice, recessive yellow mice, and albino hairless mice, does not promote UVB-induced carcinogenesis nor wrinkle formation because pre-irradiation of I PL accelerated removal of cyclobutane pyrimidine dimer (CPD)s and enhanced UVB-induced apoptotic changes. To clarify whether the effect of IPL on these phenomena depends on the repair of DNA damages, we generated mice which are deficient in DNA repair by backcrossing BHSCF, YHSCF and WHSCF mice with XPA knockout mice. Pre-irradiation of IPL at doses of 0.90 J/cm2 (BHSCF mice) and 6.30 J/cm2 (YHSCF mice and WHSCF mice) on XPA-KO mice before or after UVB irradiation at doses of 1 J/cm2 for BHSCF, 0.1 J/cm2 for YHSCF, and 0.06 J/cm2 for WHSCF, accelerated removal of CPDs and enhanced apoptotic changes which were evaluated by TUNEL staining. These results indicate that the enhancement of UVB-induced apoptosis and acceleration of removal of CPDs by pre- or post-irradiation of IPL does not depend on the repair of DNA damages.