The status of DNA synthesis and the effect of UV radiation on the DNA synthesis were studied in mouse skin by microautoradiography. Mice exposed to 100mJ/cm of UVB were injected intradermally with tritiated thymidine, 5 minutes, 2, 6 and 24 hours after irradiation and biopsies were processed for light microscopic autoradiography, A total of 25 ICR female albino haired mice were used as subjects. We compared heavily labeled cells(>10 grains/nucleus) and sparsely labeled cells (3-10 grains/nucleus) in UVL irradiated skin with nonirradiated control skin. 1. Within 5 minutes after UVL exposure an apparent depression in the number of heavily labeled cells occurred. This reduction was statistically significant and remained so for at least six hours post,irradiation. By 24 hours after UVL exposure, the reduction was recovered to nearly control level. 2. By five minutes after UVL exposure, sparsely labeled cells were observed in basal cell layer and differentiated cell layer. The nurriber of sparsely labeled cells appeared highest at five minutes after UVL exposure and then tended to fall to nearly control level at 24 hours. This aberrant type of TdR H incorporation is thought to represent unscheduled DNA synthesis to repair pyrimidine dimers formed in UVL injured DNA molecules,
Animals ; Autoradiography* ; Biopsy ; Depression ; DNA* ; Female ; Hair ; Humans ; Mice* ; Pyrimidine Dimers ; Skin* ; Thymidine ; Ultraviolet Rays

Equol, an isoflavonoid metabolite produced from the dietary isoflavone daidzein by the gut microflora in mammals, has been found to protect not only against ultraviolet (UV) radiation-induced cutaneous inflammation and photoimmune suppression, but also have antiphotocarcinogenic properties in mice. Because the state of DNA damage has been correlated with suppression of the immune system and photocarcinogenesis, we have therefore examined the potential of equol to offer protection from solar-simulated UV (SSUV) radiation-induced DNA damage in hairless mice by the immunohistochemical approach using monoclonal antibody specific for cyclobutane pyrimidine dimers (CPDs; H3 antibody). Topical application of 20 micrometer equol lotion, which was applied both before and after SSUV significantly reduced the number of CPDs. This reduction was evident immediately after SSUV exposure, at 1 h after exposure, and at 24 h after exposure, revealing 54%, 50%, and 26% reduction in CPDs, respectively. When the same concentration was applied for 5 consecutive days after SSUV exposure, there was no significant difference in the reduction of CPDs immediately after SSUV irradiation or at 1 hour afterwards, but there were significant reductions of 23% and 42% at 24 and 48 h after SSUV exposure, respectively. Despite apparently reducing the number of CPDs post-SSUV, topically applied equol did not appear to increase the rate of dimer removal. To conclude, equol applied topically prior to SSUV irradiation offers protection against CPD formation in hairless mice, possibly by acting as a suncreen and thus inhibiting DNA photodamage.
Administration, Topical ; Animals ; DNA/drug effects/radiation effects ; *DNA Damage ; Female ; Immunohistochemistry ; Isoflavones/*pharmacology ; Mice ; Mice, Inbred HRS ; Pyrimidine Dimers/metabolism ; Skin/drug effects/metabolism/*radiation effects ; Sunlight/adverse effects ; Ultraviolet Rays/*adverse effects