Immunosuppressant FTY720 Induces Apoptosis by Direct Induction of Permeability Transition and Release of Cytochrome c from Mitochondria

Abstract

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.

Coordinate Involvement of Cell Cycle Arrest and Apoptosis Strengthen the Effect of FTY720

“…6A, p27 in HL-60RG and both types of Jurkat cells was increased during 2-3 h of treatment with FTY720, but the p21 level in both types of Jurkat cells was not increased, and in fact decreased after 6 h of treatment with FTY720. This may have been the result of caspase-3-mediated cleavage, since FTY720 has been shown to activate caspase-3 within 3 h. 25,28) We could not detect p21 in HL-60RG cells, in agreement with the previous report. 29) Further confirmation of the FTY720-induced p27 increase to CDKs kinase activity was sought.…”

“…This can be explained by our previous finding that FTY720 perturbs mitochondria directly and thereby initiates the process of apoptosis. 25) In the present study, however, particularly after early incubation with FTY720 (2-3 h), cell death occurred specifically in the G0/G1 phase, and G2/M phase cells seemed to be protected against the action of FTY720. It has been demonstrated that Bcl-2 protein can be phosphorylated, resulting in a change of its function.…”

“…Inhibition of mitochondrial permeability transition as mentioned above by overexpression of the anti-apoptotic endogenous molecule Bcl-2 prevented all FTY720-induced apoptotic events in intact cells and in a cell-free system with isolated mitochondria, suggesting that the mitochondria mediated apoptotic pathway is the main pathway for FTY720-induced apoptosis. 25) However, little is known about the effect of FTY720 on cell growth, i.e., on cell cycle regulation.…”

Mycobacterium tuberculosis Virulence Correlates with Mitochondrial Cytochrome c Release in Infected Macrophages

“…Most studies on mitochondrial involvement in cell death have been performed on drug-induced models of apoptosis [22], and the association between mitochondrial alterations and infection has only recently been explored. It has been shown that Pseudomonas aeruginosa induces apoptosis by a JKN-and also by a Dc m -dependent mechanism [23].…”

Mechanism of mitochondrial 7A6 antigen exposure triggered by distinct apoptotic pathways: Involvement of caspases

“…We used anti-Fas antibody as a model inducer of receptor-mediated apoptosis, and FTY720 for mitochondria-mediated apoptosis. FTY720 directly perturbs the mitochondrial membrane potential pore to decrease DW m and release cytochrome c, leading to caspase activation and DNA fragmentation (19).…”