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.
Original language | English |
---|---|
Pages (from-to) | 411-419 |
Number of pages | 9 |
Journal | Experimental and Molecular Medicine |
Volume | 36 |
Issue number | 5 |
DOIs | |
Publication status | Published - 2004 Oct 31 |
Keywords
- Apoptosis
- Ceramide
- DMS
- Radiosensitivity
ASJC Scopus subject areas
- Biochemistry
- Molecular Medicine
- Molecular Biology
- Clinical Biochemistry