Cellular responses and gene expression profile changes due to bleomycin-induced DNA damage in human fibroblasts in space

PLoS One. 2017 Mar 1;12(3):e0170358. doi: 10.1371/journal.pone.0170358. eCollection 2017.

Abstract

Living organisms in space are constantly exposed to radiation, toxic chemicals or reactive oxygen species generated due to increased levels of environmental and psychological stresses. Understanding the impact of spaceflight factors, microgravity in particular, on cellular responses to DNA damage is essential for assessing the radiation risk for astronauts and the mutation rate in microorganisms. In a study conducted on the International Space Station, confluent human fibroblasts in culture were treated with bleomycin for three hours in the true microgravity environment. The degree of DNA damage was quantified by immunofluorescence staining for γ-H2AX, which is manifested in three types of staining patterns. Although similar percentages of these types of patterns were found between flight and ground cells, there was a slight shift in the distribution of foci counts in the flown cells with countable numbers of γ-H2AX foci. Comparison of the cells in confluent and in exponential growth conditions indicated that the proliferation rate between flight and the ground may be responsible for such a shift. We also performed a microarray analysis of gene expressions in response to bleomycin treatment. A qualitative comparison of the responsive pathways between the flown and ground cells showed similar responses with the p53 network being the top upstream regulator. The microarray data was confirmed with a PCR array analysis containing a set of genes involved in DNA damage signaling; with BBC3, CDKN1A, PCNA and PPM1D being significantly upregulated in both flight and ground cells after bleomycin treatment. Our results suggest that whether microgravity affects DNA damage response in space can be dependent on the cell type and cell growth condition.

MeSH terms

  • Bleomycin / adverse effects*
  • Bleomycin / pharmacology
  • Cell Line
  • DNA Damage*
  • Fibroblasts / metabolism*
  • Gene Expression Regulation / drug effects*
  • Humans
  • Oligonucleotide Array Sequence Analysis / methods
  • Space Flight
  • Weightlessness*

Substances

  • Bleomycin

Grants and funding

This work was supported by the NASA Fundamental Space Biology Program. The project was supported by BioServe Space Technologies. We thank Ashleigh Ruggles and Satyanand Narayan of NASA Kennedy Space Center, and Kevin Sato of NASA Ames Research Center for the support during various phases of the project. This study involved participation of personnel from two commercial companies, Wyle Laboratories and BioServe. Wyle Laboratories is a NASA contractor and employs one of the coauthors (YZ). YZ performed the gene expression data analysis for the study. BioServe (LS) was the implementation partner for this spaceflight study and received funds from NASA to support the project. LS was responsible for the hardware development, and contributed to the study design. NASA was the funding agency of the study. The funder provided support in the form of salaries for TL, YZ, YK, AF, LS, FK, and HW, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.