Decreased DNA repair activity in sunburn cells. A possible pathogenetic factor of the epidermal sunburn reaction.

The pathogenesis of the formation of sunburn cells is unknown. Based on autoradiographic methods the unscheduled DNA repair synthesis of UV-induced thymin dimers was investigated in vivo in sunburn cells and in irradiated but histologically normal stratum spinosum cells. The results show a significant lower number of sparsly labeled cells in the sunburn cell-population (13.2 +/- 2.5; mean) when compared to the population of normal stratum spinosum cells (57.8 +/- 7.5; mean). These data indicate that the population of those epidermal cells, which become manifest as sunburn cells 24 h after UV exposure exhibit a reduced DNA repair of UV induced thymine dimers immediately after UV irradiation. Nuclear factors thus seem to play at least some role in the origin of sunburn cells.