Rapid lupus autoantigen relocalization and reactive oxygen species accumulation following ultraviolet irradiation of human keratinocytes

Objective. In vitro treatment with ultraviolet B (UVB) induces relocalization of lupus autoantigens to the cell surface. We have addressed the relationship between autoantigen relocalization, accumulation of intracellular reactive oxygen species (ROS) and the induction of apoptosis following UVA and UVB exposure. Methods. Human primary keratinocytes were exposed in vitro to doses of UVA and UVB equivalent to 0.01-4 times the minimal erythemal dose. The cellular locations of Ro60, Ro52, Sm, U2-B " and La were determined using monoclonal antibodies. ROS accumulation and apoptosis induction were assessed using the intracellular ROS probe 2'7'-dichlorodihydrofluorescein diacetate, and the viability stains Hoechst 33342 and propidium iodide. Results. UV treatment induced the relocalization of all five autoantigens investigated and an accumulation of ROS. WA and UVB induced necrosis and apoptosis, respectively. Conclusion. These data suggest that both UVA and UVB induce ROS within keratinocytes but have significantly different effects upon autoantigen relocalization and cell viability.