Abstract
Ceramide generated from sphingomyelin in response to ionizing radiation has been implicated as a second messenger to induce cellular proapoptotic signals. Both ceramide and its metabolic inhibitor, N, N-dimethyl-D-erythro-sphingosine (DMS), might lead to sustained ceramide accumulation in cells more efficiently, thereby sensitizing them to γ-radiation-induced cell death. To delineate this problem, the clonogenic survival of Lewis lung carcinoma (LLC) cells was evaluated following exposure to radiation together with or without C2-ceramide, DMS, or both. The treatment of ceramide/DMS synergistically decreased the survival of the irradiated cells compared with treatment with ceramide or DMS alone. Ceramide/DMS-treated cells displayed several apoptotic features after γ-irradiation, including increased sub G1 population, TUNEL-positive fraction, and poly-(ADP-ribose) polymerase (PARP) cleavage. We also observed ceramide/ DMS induced disruption of mitochondrial membrane potential (MMP) and activation of caspase- 9 and -3 in a radiation-dose-dependent manner. Furthermore, pretreatment of LLC cells with ceramide/DMS not only increased the protein expression level of Bax, but also decreased Bcl-2 after γ-irradiation. Taken together, the present study indicates that the radiosensitizing activity of ceramide/DMS on LLC cells most likely reflects the dominance of pro-apoptotic signals related to the mitochondria-dependent pathway.
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This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Park, HW., Song, JY., Kim, KS. et al. Enhancement of radiosensitivity by combined ceramide and dimethylsphingosine treatment in lung cancer cells. Exp Mol Med 36, 411–419 (2004). https://doi.org/10.1038/emm.2004.53
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DOI: https://doi.org/10.1038/emm.2004.53