Immunosuppressant FTY720 induces apoptosis by direct induction of permeability transition and release of cytochrome c from mitochondria.
FTY720 has immunosuppressive activity in experimental organ transplantation and shows a prompt and protracted decrease of blood T lymphocytes upon oral administration. The blood lymphocyte decrease in vivo was mainly a result of FTY720-induced apoptosis. However, this apoptotic mechanism is not well understood. We examined the mechanism of FTY720-induced apoptosis in lymphoma. Western blotting and fluorescent caspase-specific substrate revealed that caspase-3 is involved in FTY720-induced apoptosis, whereas caspase-1 is not. Apoptotic cell death was inhibited by the pan-caspase inhibitor, Z-VAD-FMK, suggesting that caspase activation is essential for FTY720-induced apoptosis. FTY720 reduced mitochondrial transmembrane potential and released cytochrome c from the mitochondria of intact cells as well as in a cell-free system even in the presence of Z-VAD-FMK. As these mitochondrial reactions occurred before caspase activation, we concluded that FTY720 directly influences mitochondrial functions. The inhibition of mitochondrial permeability transition by Bcl-2 overexpression or by chemical inhibitors prevented all apoptotic events occurring in intact cells and in a cell-free system. Moreover, using a cell-free system, FTY720 did not directly affect isolated nuclei or cytosol. These results indicate that FTY720 directly affects mitochondria and triggers permeability transition to induce further apoptotic events.
Nagahara
Y
Y
Division of Research Promotion, National Children's Medical Research Center, Tokyo, Japan. Chiba, Japan.
Ikekita
M
M
Shinomiya
T
T
D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D000068876:Fingolimod Hydrochloride; D018922:HL-60 Cells; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D019169:Jurkat Cells; D008564:Membrane Potentials / Q000187:drug effects / Q000276:immunology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D011409:Propylene Glycols / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives
D003574:Cytochrome c Group; D007166:Immunosuppressive Agents; D011409:Propylene Glycols; D019253:Proto-Oncogene Proteins c-bcl-2; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine