POSSIBLE ROLE OF CUTANEOUS METALLOTHIONEIN IN PROTECTION AGAINST PHOTOOXIDATIVE STRESS - EPIDERMAL LOCALIZATION AND SCAVENGING ACTIVITY FORSUPEROXIDE AND HYDROXYL RADICALS

It is reported that increasing metallothionein (MT) synthesis suppress ed sunburn cell formation in the mouse skin after ultraviolet B (UVB) irradiation, implying a photo-protective effect of the cysteine-rich p rotein. To understand the mechanism of the defense by cutaneous MT aga inst UVB injury, an immunohistological localization of MT in human nor mal skin was studied following examination of lesional skin. MT in the skin was localized in granular layer with diffuse staining pattern in normal skin, defect in psoriatic lesions, positive but thin in granul ar cells in the lesions of lichen planus. MT treatment showed a signif icant decrease in chemiluminescence induced by superoxide radicals and depressed signal intensity of hydroxyl radicals derived from the Fent on reaction system. From the viewpoint of characteristic localization and probable role in scavenging activity for reactive oxygen species, MT in the epidermis may contribute to the protection against phototoxi c injury in association with enzymatic and non-enzymatic antioxidants. These findings may support the previous results of UV defense by cadm ium-induced MT in the skin.