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T cell selective apoptosis by a novel immunosuppressant, FTY720, is closely regulated with Bcl-2
Yukitoshi Nagahara1, Masahiko Ikekita, Takahisa Shinomiya
1Division of Radio Isotopes and Biosafety Research, National Research Institute for Child Health and Development, 3-35-31 Taishido, Setagaya-ku, Tokyo 154-8567, Japan.
Abstract:
1. A novel immunosuppressant FTY720 caused a significant decrease in peripheral T lymphocytes, but not in B lymphocytes upon oral administration. This decrease was mainly a result of FTY720-induced apoptosis. In this study, we confirmed FTY720-induced T cell selective apoptosis using lymphoma cell lines in vitro. 2. Viability loss, DNA fragmentation, Annexin V binding, and caspases activation (caspase-3, -8, and -9) were observed in Jurkat cells (T lymphoma cells), but not significantly in BALL-1 cells (B lymphoma cells). These results indicated that FTY720 selectively induced apoptosis in T cell lymphoma to a greater extent than in B cell lymphoma, a finding that is similar to the result observed when FTY720 was treated with T lymphocytes and B lymphocytes in vitro. 3. FTY720 released cytochrome c from mitochondria in Jurkat intact cells as well as from isolated Jurkat mitochondria directly, but not from mitochondria in BALL-1 cells nor from isolated BALL-1 mitochondria. 4. BALL-1 cells and B cells had more abundant mitochondria-localized anti-apoptotic protein Bcl-2 than did Jurkat cells and T cells. 5. FTY720-induced apoptosis is inhibited by the overexpression of Bcl-2, suggesting that the cellular Bcl-2 level regulates the sensitivity to FTY720.
Insights
The novel immunosuppressant FTY720 selectively induces apoptosis in T cells, not B cells, by triggering mitochondrial cytochrome c release. Bcl-2 protein levels regulate this T cell-selective response.
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- FTY720 (fingolimod) is an immunosuppressant known to reduce peripheral T lymphocytes.
- The mechanism underlying FTY720's T cell selectivity requires further elucidation.
- Understanding selective apoptosis induction is crucial for targeted immunomodulation.
Purpose of the Study:
- To investigate the mechanism of FTY720-induced apoptosis in T cells versus B cells.
- To confirm T cell-selective apoptosis using lymphoma cell lines in vitro.
- To explore the role of mitochondria and Bcl-2 in FTY720's mechanism of action.
Main Methods:
- Treatment of Jurkat (T lymphoma) and BALL-1 (B lymphoma) cell lines with FTY720.
- Assessment of apoptosis markers: viability, DNA fragmentation, Annexin V binding, caspase activation.
- Mitochondrial assays: cytochrome c release from intact cells and isolated mitochondria.
- Analysis of Bcl-2 protein expression in mitochondria.
Main Results:
- FTY720 induced significant apoptosis in Jurkat cells but not BALL-1 cells.
- T cell apoptosis involved caspase activation and mitochondrial cytochrome c release, absent in B cells.
- BALL-1 cells and B cells exhibited higher levels of anti-apoptotic Bcl-2 in mitochondria compared to Jurkat cells and T cells.
- Overexpression of Bcl-2 inhibited FTY720-induced apoptosis, indicating its regulatory role.
Conclusions:
- FTY720 selectively induces apoptosis in T cells, mediated by mitochondrial pathways.
- Differential expression of Bcl-2 in T versus B cells contributes to FTY720's selective toxicity.
- These findings provide insights into the targeted immunomodulatory potential of FTY720.