Delayed Cardiomyocyte Response to Total Body Particle Radiation Exposure - Identification of Regulatory Gene Network [iron]

We examined molecular responses using transcriptome profiling in isolated left ventricular murine cardiomyocytes to 90 cGy 1 GeV proton (1H) and 15 cGy 1 GeV/nucleon (n) iron (56Fe) particles 1 3 7 14 and 28 days after exposure. Unsupervised clustering analysis of gene expression segregated samples according to the radiation (IR) response and time after exposure with 56Fe-IR showing the greatest level of gene modulation. 1H-IR exposures showed little differential transcript modulation. Network analysis categorized the major differentially expressed genes into cell cycle oxidative responses and transcriptional regulation functional groups. Transcriptional networks identified key nodes regulating expression. Individual transcription factors were inferred to be active at 1 3 7 14 and 28 days after exposure. Validation of the signal transduction network by protein analysis showed that particle IR clearly regulates a long lived signaling mechanism for p38 MAPK signaling and NFATc4 activation. Electrophoresis mobility shift assays supported the role of additional key transcription factors GATA-4 STAT-3 and NF-kB as regulators of the response at specific time points. These data suggest that the molecular response to 56Fe-IR is unique and shows long-lasting gene expression in cardiomyocytes up to 28 days after exposure. Additionally proteins involved in signal transduction and transcriptional activation via DNA binding play a role in the response to high charge (Z) and energy (E) particles (HZE). Our study may have implications for NASA s efforts to develop heart disease risk estimates for astronauts safety via identification of specific HZE-IR molecular markers and for patients receiving conventional and particle radiotherapy. Transcriptome profiling in isolated left ventricular murine cardiomyocytes to 90 cGy 1 GeV proton (1H) and 15 cGy 1 GeV/nucleon (n) iron (56Fe) particles 1 3 7 14 and 28 days after exposure.