SUNSCREENS AND T4N5 LIPOSOMES DIFFER IN THEIR ABILITY TO PROTECT AGAINST ULTRAVIOLET-INDUCED SUNBURN CELL-FORMATION, ALTERATIONS OF DENDRITIC EPIDERMAL-CELLS, AND LOCAL SUPPRESSION OF CONTACT HYPERSENSITIVITY

Exposure of skin to ultraviolet (UV) radiation can lead to diverse bio logic effects, including inflammation, sunburn cell formation, alterat ions of cutaneous immune cells, and impaired induction of contact hype rsensitivity responses. The molecular mechanisms of these UV-induced e ffects are not completely understood. We investigated the ability of s unscreens and liposomes containing the DNA excision repair enzyme T4 e ndonuclease V to prevent these effects of UV radiation. The use of T4N 5 liposomes, which increase the repair of cyclobutyl pyrimidine dimers , provides an approach for assessing the role of DNA damage in the eff ects of UV radiation on the skin. Exposing C3H mice to 500 mJ/cm(2) UV B radiation from FS40 sunlamps resulted in skin edema, sunburn cell fo rmation, and morphologic alterations and decreased numbers of Langerha ns cells and Thy-1(+) dendritic epidermal T cells. In addition, the in duction of contact hypersensitivity after application of 2,4-dinitrofl uorobenzene on UV-irradiated skin was diminished by 80%. Applying suns creens containing octyl-N-dimethyl-p-aminobenzoate, 2-ethylhexyl-p-met hoxycinnamate, or benzophenone-3 before this dose of UV irradiation ga ve nearly complete protection against all of these effects of UV irrad iation. In contrast, topical application of T4N5 liposomes after UV ir radiation had no effect on UV-induced skin edema and only partially pr otected against sunburn cell formation and local suppression of contac t hypersensitivity, although its ability to protect against alteration s in dendritic immune cells was comparable to that of the sunscreens. These results suggest that DNA damage is involved in only some of the local effects of UV radiation on the skin. In addition, T4N5 Liposomes may be a useful adjunct to sunscreens because they can reduce some of the deleterious effects of UV radiation on skin even after a sunburn has been initiated.