title: Ultraviolet A radiation induces rapid apoptosis of human leukemia cells by Fas ligand-independent activation of the Fas death pathways.
abstract: Endogenous cellular chromophores absorb ultraviolet A radiation (UVA, 290-320 nm), the major UV component of terrestrial solar radiation, leading to the formation of reactive oxidizing species that initiate apoptosis, gene expression and mutagenesis. UVA-induced apoptosis of T helper cells is believed to underlie the UVA phototherapy for atopic dermatitis and other T cell-mediated inflammatory skin diseases. We have evaluated the involvement of the Fas-Fas ligand (FasL) pathway in rapid UVA-induced apoptosis in human leukemia HL-60 cells. UVA-induced apoptosis was not inhibited by pretreatment with a neutralizing anti-Fas antibody, although the same UVA treatment initiated cleavage of caspase-8 and subsequent processing of Bid and caspase-3-like proteases. Inhibition of caspase-8 by Lle-Glu (OMe)-Thr-Asp(OMe)-fluoromethyl ketone completely blocked caspase-3 cleavage and apoptosis in UVA-treated cells, suggesting that apoptosis was initiated by the Fas pathway. This inference was supported by demonstrating that immunoprecipitates obtained from UVA-treated cells using anti-Fas antibody contained caspase-8 and Fas-associating protein with death domain (FADD). In addition, Fas clustering in response to UVA treatment was observed by immunofluorescence microscopy. These data support a mechanism for rapid, UVA-induced apoptosis in HL-60 cells involving initial formation of the Fas-FADD-caspase-8 death complex in an FasL-independent manner.
authors.affiliation: Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Shougang
authors.initials: S
authors.lastname: Zhuang
authors.forename: Irene E
authors.initials: IE
authors.lastname: Kochevar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D018922:HL-60 Cells; D006801:Humans; D007938:Leukemia / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction; D014466:Ultraviolet Rays; D015854:Up-Regulation; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C505533:FADD protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D008562:Membrane Glycoproteins; D019014:fas Receptor; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases