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PrPC-dependent hematopoietic homeostasis radioprotection of hematopoietic progenitors
known to be cell-intrinsic,33,34 the underlying mechanisms are not fully understood. The results presented here indi- cate a significant involvement of PrPC in the age-depen- dent increase in HSC frequency. This increase may be accounted for by a PrPC-dependent upregulation of Ape1 repair activity. Independently of its DNA repair activity,35,36 Ape1 has a redox activity shown to be necessary for nor- mal embryonic hematopoiesis,37 stem cell pool mainte- nance,38,39 and hematopoietic progenitor colony formation.40 Thus, the PrPC-dependent stimulation of the Ape1 DNA repair activity might contribute to hematopoi- etic homeostasis.
We found a modest but recurrent radiation sensitiza- tion of Prnp KO mice that contrasts with a previous study showing that the absence of PrPC protected rather than sensitized mice to an 8 Gy TBI.41 However, this work was performed on a mixed 129/C57BL6 background, whereas we used a pure C57BL6 background. Furthermore, that study used a dose of X rays that was lethal for WT ani- mals, while we used different doses of non-lethal γ-rays. BM myeloid cells are particularly sensitive to chemical and radiation cytotoxicity.4,42,43 Accordingly, we found a dramatic decrease in BM myeloid progenitors within the first 24 h after radiation exposure that was exacerbated in Prnp KO irradiated mice. The reduced frequency of KO irradiated myeloid progenitors was associated with high- er CMP and GMP apoptosis, within the first 12 h after irradiation, as well as with an absence of stimulation of Ape1 activity in these subpopulations 1 h after irradia- tion. In contrast, in WT irradiated myeloid progenitors and HSC, upregulation of Prnp gene expression was asso-
ciated with an increase in Ape1 activity in these subpop- ulations. PrPC has been shown to protect HSC from myelotoxic injury by 5-FU, commonly used in chemotherapy,25 and we now extend its myeloprotective role to radiotherapy.
Finally, a similar basal reduced number of myeloid pro- genitors and a similar radiation sensitivity of myeloid progenitors were found in the co-isogenic PrnpZH3/ZH3 mouse line44 and the Prnp-/- mouse line. These results rule out the involvement of any Prnp flanking gene polymor- phism previously described by Nuvolone et al.45
Altogether, these results suggest that PrPC is involved in the homeostasis of steady-state hematopoiesis and that PrPC-dependent activation of base excision repair contributes to the radioprotection of the myeloid progen- itors of the mouse bone marrow.
Acknowledgments
The authors thank Véronique Neuville and staff of the IRCM animal facility for animal care and breeding, and Petra Schwarz for managing Prnp ZH3/ZH3 mice supply. Flow cytometry and cell sorting were performed at the IRCM Flow Cytometry Shared Resource, established by equipment grants from DIM-Stem-Pôle, INSERM, Foundation ARC, and CEA.
Funding
This work was supported by the French National Electricity Company (EDF), the Transverse Division N°4 (Segment n°4 Radiobiologie – headed by Christophe Carles) and the Radiobiology Program of the French Alternative Energies and Atomic Energy Commission (CEA).
References
1. Dörr H, Meineke V. Acute radiation syn- drome caused by accidental radiation expo- sure - therapeutic principles. BMC Med. 2011;9(1):126.
2. Simonnet AJ, Nehmë J, Vaigot P, Barroca V, Leboulch P, Tronik-Le Roux D. Phenotypic and functional changes induced in hematopoietic stem/progenitor cells after gamma-ray radiation exposure. Stem Cells. 2009;27(6):1400-1409.
3. Shao L, Luo Y, Zhou D. Hematopoietic Stem Cell Injury Induced by Ionizing Radiation. Antioxid Redox Signal. 2014;20(9):1447-1462.
4. DownJD,BoudewijnA,vanOsR,Thames HD, Ploemacher RE. Variations in radiation sensitivity and repair among different hematopoietic stem cell subsets following fractionated irradiation. Blood. 1995; 86(1):122-127.
5. Mohrin M, Bourke E, Alexander D, et al. Hematopoietic stem cell quiescence pro- motes error-prone DNA repair and mutage- nesis. Cell Stem Cell. 2010;7(2):174-185.
6. Kim JH, Thimmulappa RK, Kumar V, et al. NRF2-mediated Notch pathway activation enhances hematopoietic reconstitution fol- lowing myelosuppressive radiation. J Clin Invest. 2014;124(2):730-741.
7. Zachman DK, Leon RP, Das P, et al. Endothelial cells mitigate DNA damage and promote the regeneration of hematopoietic stem cells after radiation injury. Stem Cell Res. 2013;11(3):1013-1021.
8. Ensminger M, Iloff L, Ebel C, Nikolova T, Kaina B, Löbrich M. DNA breaks and chro- mosomal aberrations arise when replica- tion meets base excision repair. J Cell Biol. 2014;206(1):29-43.
9. Bauer NC, Corbett AH, Doetsch PW. The current state of eukaryotic DNA base dam- age and repair. Nucleic Acids Res. 2015; 43(21):10083-10101.
10. Fung H, Demple B. Distinct roles of Ape1 protein in the repair of DNA damage induced by ionizing radiation or bleomycin. J Biol Chem. 2011;286(7):4968- 4977.
11. Wang H, Wang X, Chen G, et al. Distinct roles of Ape1 protein, an enzyme involved in DNA repair, in high or low linear energy transfer ionizing radiation-induced cell killing. J Biol Chem. 2014;289(44):30635- 30644.
12. Laev SS, Salakhutdinov NF, Lavrik OI. Inhibitors of nuclease and redox activity of apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1). Bioorganic Med Chem. 2017;25(9):2531-2544.
13. Parsons JL, Dianova II, Dianov GL. APE1 is the major 3 -phosphoglycolate activity in human cell extracts. Nucleic Acids Res. 2004;32(12):3531-3536.
14. Vasko MR, Guo C, Thompson EL, Kelley MR. The repair function of the multifunc- tional DNA repair/redox protein APE1 is neuroprotective after ionizing radiation. DNA Repair (Amst). 2011;10(9):942-952.
15. Ströbel T, Madlener S, Tuna S, et al. Ape1 guides DNA repair pathway choice that is
associated with drug tolerance in glioblas-
toma. Sci Rep. 2017;7(1):1-13.
16. Prusiner SB. Novel proteinaceous infectious
particles cause scrapie. Science. 1982;
216(4542):136-144.
17. Milhavet O, Lehmann S. Oxidative stress
and the prion protein in transmissible spongiform encephalopathies. Brain Res Brain Res Rev. 2002;38(3):328-339.
18. Rachidi W, Vilette D, Guiraud P, et al. Expression of prion protein increases cellu- lar copper binding and antioxidant enzyme activities but not copper delivery. J Biol Chem. 2003;278(11):9064-9072.
19. McLennan NF, Brennan PM, McNeill A, et al. Prion protein accumulation and neuro- protection in hypoxic brain damage. Am J Pathol. 2004;165(1):227-235.
20. Krebs B, Wiebelitz A, Balitzki-Korte B, et al. Cellular prion protein modulates the intra- cellular calcium response to hydrogen per- oxide. J Neurochem. 2007;100(2):358-367.
21. Bravard A, Auvré F, Fantini D, et al. The prion protein is critical for DNA repair and cell survival after genotoxic stress. Nucleic Acids Res. 2015;43(2):904-916.
22. Kent DG, Copley MR, Benz C, et al. Prospective isolation and molecular charac- terization of hematopoietic stem cells with durable self-renewal potential. Blood. 2009;113(25):6342-6350.
23. Liu T, Li R, Wong B-S, et al. Normal Cellular Prior Protein Is Preferentially Expressed on Subpopulations of Murine Hemopoietic Cells. J Immunol. 2001;166 (6):3733-3742.
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