Abstract
Objective: We previously reported that adenosine-induced apoptosis in HL-60 cells was attenuated by cotreating the cells with pyrimidine nucleosides. The mechanism involved in this adenosine-induced apoptosis by the differential supply of nucleosides is studied here with a particular focus on the regulation of apoptosis-associated mitochondrial events. Methods: Time-dependent changes in the mitochondrial membrane potential (MMP) after treatment with adenosine and/or thymidine were monitored. Results: The cells did not show any decrease of MMP level up to 2.5 h after 1 mM adenosine exposure, whereas cytochrome c release, caspase-9 and caspase-3 activity, and DNA fragmentation were already activated, suggesting that mitochondrial depolarization is not a prerequisite of other apoptosis-related mitochondrial events. In contrast, the translocation of Bax to mitochondria and the release of cytochrome c began within the first hour of adenosine treatment. Conclusion: Thus, it is believed that adenosine-induced apoptosis is mediated by the activation of the caspase cascade by cytochrome c release with concomitant increase of Bax in the mitochondria, which implies that the translocation of Bax might be a leading event in the adenosine-induced apoptosis. Moreover, we found that most of the apoptotic parameters in adenosine-induced cellular changes, such as translocation of Bax, the release of cytochrome c, and the consequent activation of caspase-9 and caspase-3, were attenuated by thymidine supplement, thus indicating that the sensing of a nucleoside or nucleotide balance might be an upstream event of cytochrome c release. Therefore, it can be concluded that thymidine can attenuate adenosine-induced apoptosis by modulating the earliest stage of the mitochondrial apoptotic pathway.
Original language | English (US) |
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Pages (from-to) | 570-576 |
Number of pages | 7 |
Journal | Journal of Cancer Research and Clinical Oncology |
Volume | 127 |
Issue number | 9 |
DOIs | |
State | Published - 2001 |
Externally published | Yes |
Keywords
- Adenosine
- Apoptosis
- Bax translocation
- Cytochrome c
- Mitochondria
- Thymidine
ASJC Scopus subject areas
- Oncology
- Cancer Research