Long-term effects of combined exposures to simulated microgravity and galactic cosmic radiation on the mouse lung: sex-specific epigenetic reprogramming

Affiliations

¹ Department of Environmental Health Sciences, #820-11, Slot, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
² Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
³ Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
⁴ Department of Radiation Oncology, Section on Radiation Biology, Wake Forest University School of Medicine, Winston-Salem, NC, 21757, USA.
⁵ Department of Biostatistics, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
⁶ Department of Physics and Astronomy, Mary Bird Perkins Cancer Center, Louisiana State University, 439-B Nicholson Hall, Tower Dr, Baton Rouge, LA, 70803-4001, USA.
⁷ School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY, 14642, USA.
⁸ Department of Medical Physiology, College of Medicine, Medical Research and Education Building II, Texas A&M University, 8447 Riverside Pkwy, Office, 341, Bryan, TX, 77807, USA.
⁹ Department of Environmental Health Sciences, #820-11, Slot, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA. ikoturbash@uams.edu.

PMID: 39841235
PMCID: PMC12338996
DOI: 10.1007/s00411-025-01108-4

Long-term effects of combined exposures to simulated microgravity and galactic cosmic radiation on the mouse lung: sex-specific epigenetic reprogramming

Kirsten Clement et al. Radiat Environ Biophys. 2025 Mar.

. 2025 Mar;64(1):17-27.

doi: 10.1007/s00411-025-01108-4. Epub 2025 Jan 22.

Affiliations

¹ Department of Environmental Health Sciences, #820-11, Slot, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
² Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
³ Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
⁴ Department of Radiation Oncology, Section on Radiation Biology, Wake Forest University School of Medicine, Winston-Salem, NC, 21757, USA.
⁵ Department of Biostatistics, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA.
⁶ Department of Physics and Astronomy, Mary Bird Perkins Cancer Center, Louisiana State University, 439-B Nicholson Hall, Tower Dr, Baton Rouge, LA, 70803-4001, USA.
⁷ School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY, 14642, USA.
⁸ Department of Medical Physiology, College of Medicine, Medical Research and Education Building II, Texas A&M University, 8447 Riverside Pkwy, Office, 341, Bryan, TX, 77807, USA.
⁹ Department of Environmental Health Sciences, #820-11, Slot, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, 4301 W. Markham Str, Little Rock, AR, 72205, USA. ikoturbash@uams.edu.

PMID: 39841235
PMCID: PMC12338996
DOI: 10.1007/s00411-025-01108-4

Abstract

Most studies on the effects of galactic cosmic rays (GCR) have relied on terrestrial irradiation using spatially homogeneous dose distributions of mono-energetic beams comprised of one ion species. Here, we exposed mice to novel beams that more closely mimic GCR, namely, comprising poly-energetic ions of multiple species. Six-month-old male and female C57BL/6J mice were exposed to 0 Gy, 0.5 Gy, or 1.5 Gy simplified simulated 5 ion GCR (GCRsim). Exposure to microgravity was simulated using hindlimb unloading (HLU). At nine months post exposure, the mice were terminated to assess for the presence of exposure-induced epigenetic alterations. DNA hypermethylation in the 5'-untranslated regions of Lx_III, MdFanc_I, and MdMus_II families of the Long Interspersed Nucleotide Element 1 (LINE-1) was observed in the lungs of male mice. These effects were accompanied by increases in the expression of DNA methyltransferases Dnmt1 and Dnmt3a, and methyl-binding protein, MecP2. Trends towards DNA hypomethylation, although insignificant, were observed in the lungs of female mice in the HLU + 1.5 Gy GCRsim group. Altogether, our findings suggest persistent and sex-specific epigenetic reprogramming in the mouse lung and suggests that the DNA methylation status of LINE-1 can serve as a robust and reliable biomarker of previous radiation exposure.

Keywords: DNA methylation; Galactic cosmic rays; Hind-limb suspension; Ionizing radiation; LINE-1; Microgravity.

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Conflict of interest statement

Declarations. Research involving animals: All animal procedures within this study were approved by the Institutional Animal Care and Use Committees at UAMS and BNL. Competing interests: The authors declare no competing interests.

Figures

**Fig. 1**
Sex specificity on global patterns of LINE-1 DNA methylation via principal component analysis as determined by the methylation-sensitive RT-PCR in male and female mice 9 months after exposure to hind-limb unloading (HLU) and/or simulated galactic cosmic radiation (GCRsim). (a) Sham; (b) HLU; (c) GCRsim 0.5 Gy; (d) HLU + GCRsim 0.5 Gy; (e) HLU + GCRsim 1.5 Gy

**Fig. 2**
DNA methylation profiles of 10 evolutionary distinct LINE-1 elements as determined by methylation-sensitive RT-PCR in male and female mice 9 months after exposure to hind-limb unloading (HLU) and/or simulated galactic cosmic radiation (GCRsim). Fold change from control for each sample is represented by a colour change on the heatmap

**Fig. 3**
DNA methylation patterns of (a) L1MdTf_III and (b) L1Lx_III LINE-1 elements in male and female mice 9 months after exposure to hind-limb unloading (HLU) and/or simulated galactic cosmic radiation (GCRsim) as determined by the methylation-sensitive RT-PCR

**Fig. 4**
LINE-1 DNA methylation patterns in male and female 9 months after exposure to hind-limb unloading (HLU) combined with 1.5 Gy simulated galactic cosmic radiation (GCRsim) as determined by the methylation-sensitive RT-PCR

**Fig. 5**
LINE-1 ORF1 (a and b) and ORF2 (c and d) expression in male and female mice 9 months after exposure to hind-limb unloading (HLU) and/or simulated galactic cosmic radiation (GCRsim). The differential expression of genes was determined by quantitative RT-PCR. The fold change data were calculated from the ΔΔCt values

**Fig. 6**
DNA methylation machinery in male and female mice 9 months after exposure to hind-limb unloading (HLU) and/or simulated galactic cosmic radiation (GCRsim). (a and d) Dnmt1, (b and e) Dnmt3a, (c and f) MeCP2. The differential expression of genes was determined by quantitative RT-PCR. The fold change data were calculated from the ΔΔCt values

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Long-term effects of combined exposures to simulated microgravity and galactic cosmic radiation on the mouse lung: sex-specific epigenetic reprogramming

Affiliations

Long-term effects of combined exposures to simulated microgravity and galactic cosmic radiation on the mouse lung: sex-specific epigenetic reprogramming

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

MeSH terms

Grants and funding

LinkOut - more resources

Full Text Sources