Transient protection by peripheral benzodiazepine receptors during the early events of ultraviolet light-induced apoptosis

The peripheral benzodiazepine receptor (PBR) is a mitochondrial protein inv olved in the formation of mitochondrial permeability transition (PT) pores which play a critical role during the early events of apoptosis. PBRs are l ocated in many tissues and are strongly expressed in the superficial layers of human epidermis. PBRs play a protective role against free radical damag e and PER ligands modulate apoptosis, To investigate the role of PER during the early events of ultraviolet (UV)-mediated apoptosis we compared the ef fects of UVB on PBR-transfected Jurkat cells and their wild type counterpar ts devoid of any PER expression. Results indicate that early after UVB expo sure (up to 4 h), PBR-transfected cells were more resistant to apoptosis an d exhibited a delayed mitochondrial transmembrane potential drop, a diminis hed superoxide anions production, and a reduced caspase-3 activation. Taken together these findings suggest that PER may regulate early death signals leading to UV induced apoptosis.