Moon MS, Kim JS, Kim TL, Yum JJ, Cho EW, Kim IG. Polyamine depletion partially reduces the radiation-induced cell death via cell cycle delay mediated by thioredoxin.
Cell Biol Toxicol 2006;
22:137-47. [PMID:
16532286 DOI:
10.1007/s10565-006-0042-z]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Accepted: 01/05/2006] [Indexed: 11/29/2022]
Abstract
In previous studies, polyamine depletion by DFMO (alpha-difluoromethylornithine)-treatment reduced H(2)O(2)-induced apoptotic cell death by reduction of ferric ion uptake. In the present study, we analyzed the reduction of radiation-induced cell death by polyamine depletion. Exposure of HT29 cells to radiation induced severe cell death, but when cells were pretreated with DFMO, a specific inhibitor of polyamine biosynthesis, radiation-induced cell death was reduced to 50-60% of control. Cell cycle analysis showed that, in these cells, the time to reach the G(2)/M phase arrest was delayed for 20-24 h compared to the control cells, at which stage the fate of cells exposed to ionizing radiation is determined. DFMO-treated cells also showed a low level of thioredoxin, which is a high-level determinant of the cellular fate. To investigate the relationship between the G(2)/M phase arrest and the reduction of thioredoxin caused by polyamine depletion, we also analyzed thioredoxin-antisensed (asTRX) HT29 cells as for DFMO-treated cells. In asTRX-transfected cells, the gamma-irradiation-induced G(2)/M phase arrest was also significantly delayed and radiation-induced cell death was profoundly reduced, as in the DFMO-treated cells. Both sets of cells showed a decrease of cyclin D1 and an increment of HSP25, which are involved in radiation-induced cell cycle progress. Overall, these results suggest that polyamines are essential for normal cell death of HT29 cells triggered by gamma-radiation and that this is partially mediated by the regulation of thioredoxin expression.
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