Journal
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY
Volume 87, Issue 1, Pages 24-35Publisher
TAYLOR & FRANCIS LTD
DOI: 10.3109/09553002.2010.518206
Keywords
particle radiation; solar flare; T lymphocytes; signalling pathways; cytokines
Funding
- Low Dose Radiation Research Program
- Office of Science, U.S. Department of Energy [DE-FG02-05ER64098]
- NASA [NNJ06HD78A]
- LLUMC Department of Radiation Medicine
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Purpose: Astronauts on missions are exposed to low-dose/low-dose-rate (LDR) radiation and could receive high doses during solar particle events (SPE). This study investigated T cell function in response to LDR radiation and simulated SPE (sSPE) protons, alone and in combination. Materials and methods: C57BL/6 mice received LDR gamma-radiation (Co-57) to a total dose of 0.01 Gray (Gy) at 0.179 mGy/h, either with or without subsequent exposure to 1.7 Gy sSPE protons delivered over 36 h. Mice were euthanised on days 4 and 21 post-exposure. T cells with cluster of differentiation 4 (CD4(+)) were negatively isolated from spleens and activated with anti-CD3 antibody. Cells and supernatants were evaluated for survival/signalling proteins and cytokines. Results: The most striking effects were noted on day 21. In the survival pathway, nuclear factor-kappaB (NF-kappa B; total and active forms) and p38 mitogen activated protein kinase (p38MAPK; total) were significantly increased and cJun N-terminal kinase (JNK; total and active) was decreased when mice were primed with LDR gamma-rays prior to sSPE exposure (P < 0.001). Evaluation of the T cell antigen receptor (TCR) signalling pathway revealed that LDR gamma-ray exposure normalised the high sSPE proton-induced level of lymphocyte specific protein tyrosine kinase (Lck; total and active) on day 21 ( < 0.001 for sSPE vs. LDR + sSPE), while radiation had no effect on active zeta-chain-associated protein kinase 70 (Zap-70). There was increased production of interleukin-2 (IL-2) and IL-4 and decreased transforming growth factor-beta 1 in the LDR + sSPE group compared to the sSPE group. Conclusion: The data demonstrate, for the first time, that protracted exposure to LDR gamma-rays can significantly modify the effects of sSPE protons on critical survival/signalling proteins and immunomodulatory cytokines produced by CD4(+) T cells.
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