Ifosfamide impairs the allostimulatory capacity of human dendritic cells by intracellular glutathione depletion

Abstract

IntroductionIfosfamide, which is a commonly used antineoplastic agent in the treatment of malignancies such as lymphomas, breast cancer, and sarcomas [1][2][3] has been shown to reduce glutathione (GSH) levels in various cell types. 4,5 Previously, we demonstrated that ifosfamideinduced GSH depletion in T cells and natural killer (NK) cells was accompanied by a corresponding decrease in T-cell function and NK-cell cytotoxicity. 6,7 In vivo ifosfamide is metabolically activated by hepatic mixedfunction oxidases into 4-hydroxyifosfamide (4-OH-IF). In our studies we used the prodrug 4-hydroperoxyifosfamide (4-OOH-IF), which in aqueous solution spontaneously gives rise to pharmacologically equivalent amounts of 4-OH-IF, the activated form of ifosfamide. 8 GSH is a tripeptide consisting of glutamate, cysteine, and glycine, and it takes part in many metabolic and cell-cycledependent functions such as detoxification of free radicals and exogenous toxins, protein synthesis, transport, and maintenance of intracellular redox balance. 9 In addition to housekeeping properties, GSH influences lymphocyte proliferation, 10-12 polymorphonuclear cell function, 13 and chemokine and cytokine production by different cell types. [14][15][16] Antigen-presenting cells (APCs) derived from murine spleen have been shown to direct T-cell responses toward a T H 1-or T H 2-type response, depending on the level of intracellular glutathione. T H 2 responses occur when glutathione levels are low. 17 Suppression of tumor cell growth is favored by a T H 1 response in which cytokines such as interferon-␥ (IFN-␥) and interleukin-12 (IL-12) play important roles. 18,19 Dendritic cells (DCs) are the most potent APCs in the body, and their unique ability to stimulate a primary T-cell response places them at the center of an immune response toward tumors. 20,21 Immature DCs specialize in capturing and processing antigens, whereas mature DCs present antigenic peptides to T cells. 22 We have therefore made a comparison of the effect of 4-OH-IF on GSH levels in immature and mature DCs and monocytes with GSH levels in T cells and NK cells. In addition, we studied the effect of 4-OH-IF-induced GSH depletion on DC functional properties. We found that when comparing cells from the same donors, DCs had higher constitutive levels of GSH than T cells and NK cells and were less sensitive to GSH depletion by 4-OH-IF. Treatment of DCs with 4-OH-IF or L-buthioninesulfoximine (BSO) (which inhibits GSH biosynthesis by blocking ␥-glutamyl-cysteine synthetase) reduced the ability of immature DCs to stimulate an allogeneic response but had no effect on the ability of mature DCs to present exogenously added tyrosinase peptide to tyrosinase-specific cytotoxic T lymphocytes (CTLs). IFN-␥ production was also reduced in allogeneic cultures containing 4-OH-IF-treated DCs. 4-OH-IF also impaired the ability of DCs to produce IL-12p70 after lipopolysaccharide (LPS) and IFN-␥ stimulation. The allostimulatory capacity of DCs and the cytokine production by peripheral blood leukocyte...

Nuclear Erythroid 2 p45-Related Factor 2 Inhibits the Maturation of Murine Dendritic Cells by Ragweed Extract

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“…For example, Peterson and colleagues showed that the depletion of glutathione in murine antigen-presenting cells in vivo resulted in lower Th1 activity and higher Th2 activity (14). Other studies confirmed that DCs rely on intracellular redox state for proper development and function and that DC activation and associated immune functions are influenced by oxidative stress (15)(16)(17)(18)(19)(20)(21). Oxidative stress occurs when the oxidants overwhelm antioxidant defenses.…”

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“…134 Variations on these themes most likely result in altered function of other reconstituted immune effector cells. 135 However, such mechanisms of immune dysfunction post-HSCT currently remain largely undefined. 136 Nonetheless, consequences of immune dysfunction in the HSCT recipient include delayed engraftment or even graft failure, disease relapse, and infection.…”