title: Cellular responses and gene expression profile changes due to bleomycin-induced DNA damage in human fibroblasts in space.
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.
authors.affiliation: NASA Johnson Space Center, Houston, Texas, United States of America.|University of Houston Clear Lake, Houston, Texas, United States of America.
authors.forename: Tao
authors.initials: T
authors.lastname: Lu
authors.affiliation: NASA Kennedy Space Center, Houston, Texas, United States of America.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: NASA Johnson Space Center, Houston, Texas, United States of America.|Wyle Laboratories, Houston, Texas, United States of America.
authors.forename: Yared
authors.initials: Y
authors.lastname: Kidane
authors.affiliation: NASA Johnson Space Center, Houston, Texas, United States of America.
authors.forename: Alan
authors.initials: A
authors.lastname: Feiveson
authors.affiliation: BioServe Space Technologies, Boulder, Colorado, United States of America.
authors.forename: Louis
authors.initials: L
authors.lastname: Stodieck
authors.affiliation: NASA Ames Research Center, Moffett Field, California, United States of America.
authors.forename: Fathi
authors.initials: F
authors.lastname: Karouia
authors.affiliation: Norfolk State University, Norfolk, Virginia, United States of America.
authors.forename: Govindarajan
authors.initials: G
authors.lastname: Ramesh
authors.affiliation: University of Houston Clear Lake, Houston, Texas, United States of America.
authors.forename: Larry
authors.initials: L
authors.lastname: Rohde
authors.affiliation: NASA Johnson Space Center, Houston, Texas, United States of America.
authors.forename: Honglu
authors.initials: H
authors.lastname: Wu
mesh_terms: D001761:Bleomycin / Q000009:adverse effects* / Q000494:pharmacology; D002460:Cell Line; D004249:DNA Damage; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D013026:Space Flight; D014893:Weightlessness
chemical_list: D001761:Bleomycin