Photoactivation of pheophorbide a induces a mitochondrial-mediated apoptosis in Jurkat leukaemia cells.
The mechanism of cell death by pheophorbide a (Pba) which has been established to be a potential photosensitizer was examined in experimental photodynamic therapy (PDT) on Jurkat cells, a human lymphoid tumor cell line. In 30-60 min after irradiation, Pba treated cells exhibited apoptotic features including membrane blebbing and DNA fragmentation. Pba/PDT caused a rapid release of cytochrome c from mitochondria into the cytosol. Sequentially, activation of caspase-3 and the cleavage of poly ADP-ribose polymerase (PARP) were followed. Meanwhile, no evidence of activation of caspase-8 was indicated in the cells. In experiments with caspase inhibitors, it was found that caspase-3 alone was sufficient initiator for the Pba-induced apoptosis of the cells. Pba specific emission spectra were confirmed in the mitochondrial fraction and the light irradiation caused a rapid change in its membrane potential. Thus, mitochondria were entailed as the crucial targets for Pba as well as a responsible component for the cytochrome c release to initiate apoptotic pathways. Taken together, it was concluded that the mode of Jurkat cell death by Pba/PDT is an apoptosis, which is initiated by mitochondrial cytochrome c release and caspase-3-pathways.
Lee
Won-Young
WY
Department of Microbiology, College of Medicine, Yonsei University, CPO Box 8044, Seoul 120-752, Republic of Korea.
Lim
Dae-Seog
DS
Ko
Si-Hwan
SH
Park
Young-Jae
YJ
Ryu
Kang-Sun
KS
Ahn
Mi-Young
MY
Kim
Yong-Rok
YR
Lee
Dai Woon
DW
Cho
Chang-Whan
CW
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000528:radiation effects*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells; D008027:Light; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010778:Photochemotherapy / Q000379:methods*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D011838:Radiation-Sensitizing Agents; D002734:Chlorophyll; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C032623:pheophorbide a