Modulation of catalase in human skin in vivo by acute and chronic UV radiation

In this study, we demonstrate that catalase is differently regulated either by acute, or chronic UV radiation during the photoaging process. 2MED of U V radiation decreased the activity and expression of catalase gradually in the epidermis and dermis at between 24 and 48 h after the UV exposure. Thes e levels then returned to near normal by 72 h after exposure. The catalase mRNA was also decreased in the skin 24 h after UV irradiation to 50% of the control level, and then started to recover. In contrast, chronic UV irradi ation over a lifetime (approximately 50 years) increased the catalase activ ity in the epidermis and dermis of the human skin in vivo. Our results sugg est that catalase might be one of the important enzymes in the skin aging p rocess, and that it plays an important role in the photoprotection of the s kin from UV light.