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Effects of ifosfamide on immunocompetent effector cells
G Multhoff1, C Botzler, A Allenbacher
1Institut für Klinische Hämatologie, Munich, Germany.
Insights
Ifosfamide chemotherapy damages cytotoxic T cells by depleting glutathione (GSH), but not natural killer (NK) cells. NK cells resist ifosfamide due to higher GSH levels and cystine uptake, preserving their cytotoxic activity.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Ifosfamide is a widely used chemotherapeutic agent.
- Immunocompetent effector cells like cytotoxic T lymphocytes and natural killer (NK) cells are crucial for antitumor immunity.
- Understanding the differential effects of chemotherapy on these immune cells is vital for optimizing cancer therapy.
Purpose of the Study:
- To investigate the in vitro effects of ifosfamide's activated form (4-OH-IF) on cytotoxic T cells and NK cells.
- To determine the mechanisms underlying any observed differential sensitivity.
- To explore potential protective strategies against ifosfamide-induced immunotoxicity.
Main Methods:
- In vitro treatment of activated cytotoxic T cells and NK cells with 4-hydroperoxyifosfamide (4-OOH-IF), which generates 4-OH-IF.
- Assessment of cellular lytic activity against target cells.
- Measurement of intracellular glutathione (GSH) levels.
- Evaluation of thiol (e.g., mesna) and cystine uptake by immune cells.
Main Results:
- 4-OH-IF treatment significantly reduced the cytotoxic activity of T cells, correlating with GSH depletion.
- Thiol supplementation (mesna) restored T cell lytic activity and GSH levels.
- NK cell lytic activity remained largely unaffected by 4-OH-IF.
- NK cells exhibited higher baseline GSH levels, increased GSH synthesis rates, and cystine uptake capacity, contributing to their resistance.
- T cells lacked significant cystine uptake capability.
Conclusions:
- Cytotoxic T cells are more susceptible to ifosfamide-induced cytotoxicity than NK cells due to lower GSH levels and impaired GSH replenishment.
- NK cells possess inherent resistance mechanisms against ifosfamide, including higher GSH levels and the ability to uptake cystine.
- These findings highlight the differential immunomodulatory effects of ifosfamide and suggest strategies to mitigate T cell-mediated immunosuppression during chemotherapy.
Abstract:
We analyzed the effects of ifosfamide, a chemotherapeutic agent that is broadly used within anticancer therapy, on immunocompetent effector cell subpopulations. For our in vitro studies we used 4-hydroperoxyifosfamide (4-OOH-IF), which rapidly gives rise to 4-OH-IF, the activated form of ifosfamide. Activated cytotoxic T lymphocytes and natural killer (NK) cells were used because of their antitumor activity and their antiviral or antibacterial activity. Our study demonstrated three major findings. (1) The capacity of cytotoxic T cells to lyse their specific target cells was substantially reduced by 4-OH-IF treatment. This inhibition of the lytic activity could be correlated with a substantial depletion of the intracellular glutathione (GSH) levels. A rapid reconstitution of the depleted GSH levels and of the cytotoxic activity was achieved by incubation of the T cells with thiols such as mercaptoethanesulfonate (mesna). (2) In contrast to T cells the lytic activity of NK cells was not substantially affected by 4-OH-IF treatment; this increased resistance of NK cells against 4-OH-IF treatment could be explained by their higher initial GSH levels and by their higher rate of GSH synthesis. Furthermore, we demonstrated that (3) NK cells, but not T cells, have the capacity to take up cystine, the oxidized form of cysteine, from the medium. In conclusion we can state that NK cells are much more resistant to ifosfamide treatment compared to T cells with respect to intracellular GSH levels and cytotoxic activity.