Ultraviolet-A1 radiation induces immediate apoptosis in a human leukemia T-cell line (Jurkat)

Abstract

We previously reported that radiation from all three ultraviolet (UV) waveband regions, i.e., UVA (320-400 nm), UVB (290-320 nm), and UVC (200-290 nm) cause either immediate apoptosis (UVA1, 340-400 nm) or delayed apoptosis (UVB or UVC) in L5178Y-R murine lymphoma cells. We coined the terms immediate and delayed apoptosis to help distinguish the mechanistic differences between apoptosis and programmed cell death (or delayed apoptosis) which have been incorrectly used as synonyms. This confusion occurred primarily because these two cell death mechanisms are morphologically identical. However, kinetics can be used to discriminate between these two cell death mechanisms. Immediate apoptosis occurs within 4 h following exposure, whereas delayed apoptosis requires 20-34 h to display similar morphological changes. In this investigation, we explored the possibility that the UVA1-induced immediate apoptotic mechanism might be a common phenomenon by examining a human acute T-cell leukemia cell line (Jurkat).Four hours following either sham- or UVAl-exposure to 250, 500, or 750 kJ/m2 (resulting in approximately 50, 80 and 90% reproductive death, respectively) from a 200 W/m2 sunlamp (>340 nm), Jurkat T-cells (clone E6-1, American Type Culture Collection, Rockville, MD) were processed for transmission electron microscopy (TEM) using a procedure described previously.