Abstract
Although UV radiation has been known to induce apoptosis through an activation of signal transduction triggered by DNA damage, the responses of cells to UV radiation are quite different among different tissue sources. For example, UV causes a rapid cell death in most hematopoietic cell lines including human leukemic Jurkat cells and HeLa cells established from human cervical carcinoma show a delayed form of apoptosis following exposure to UV.
In order to know the mechanisms of cell-type dependent apoptosis, Jurkat and HeLa cells were irradiated with UV (254 nm), incubated for various time intervals after irradiation, and examined the changes in morphological and biochemical characteristics in the early stage. After UV irradiation, rapid appearance of small cells was observed in Jurkat cells, but not in HeLa cells. This phenomenon is a reflection of apoptotic volume decrease (AVR), which is observed in early stage of apoptosis and caused by the efflux of intracellular KCl. Interestingly, inhibition of K+ ion-channels with 2 mM 4-aminopyridine efficiently blocked the induction of apoptosis by UV radiation in Jurkat cells, but not in HeLa cells. These results suggest that UV irradiation causes K+ ion-channel alterations and triggers a rapid form of apoptosis in Jurkat cells.
