Modulation of tumor necrosis factor-mediated cell death by fullerenes

Abstract

Purpose. The fullerene (C60/C70 mixture—C60/70) nanocrystalline suspension prepared by solvent exchange method using tetrahydrofyran (THF/nC60/70) and polyhydroxylated C60/70 [C60/70(OH)n] were compared for their ability to modulate cytotoxicity of the proinflammatory cytokine tumor necrosis factor (TNF). Materials and Methods. TNF-induced cytotoxicity was assessed in L929 fibrosarcoma cells by crystal violet assay. The type of cell death (apoptosis/necrosis), production of reactive oxygen species, mitochondrial depolarization and caspase activation were determined by flow cytometry using the appropriate reporter dyes. Results. THF/nC60/70 augmented, while C60/70(OH)n reduced the cytotoxicity of TNF. The numbers of cells undergoing apoptosis/necrosis, as well as of those displaying the activation of apoptosis-inducing enzymes of caspase family, were respectively increased or reduced by THF/nC60/70 or C60/70(OH)n. The antioxidant N-acetylcysteine and mitochondrial permeability transition inhibitor cyclosporin A each partly blocked the cytotoxic action of TNF, indicating the involvement of oxidative stress and mitochondrial dysfunction in the TNF cytotoxicity. Accordingly, THF/nC60/70 or C60/70(OH)n potentiated or suppressed, respectively, TNF-triggered oxidative stress and mitochondrial depolarization. Conclusion. The ability of different fullerene preparations to modulate TNF-induced oxidative stress and subsequent cell death suggests their potential value in the TNF-based cancer therapy or prevention of TNF-dependent tissue damage