title: Extracellular Vesicles Mediate Radiation-Induced Systemic Bystander Signals in the Bone Marrow and Spleen.
abstract: Radiation-induced bystander effects refer to the induction of biological changes in cells not directly hit by radiation implying that the number of cells affected by radiation is larger than the actual number of irradiated cells. Recentin vitrostudies suggest the role of extracellular vesicles (EVs) in mediating radiation-induced bystander signals, butin vivoinvestigations are still lacking. Here, we report anin vivostudy investigating the role of EVs in mediating radiation effects. C57BL/6 mice were total-body irradiated with X-rays (0.1, 0.25, 2 Gy), and 24 h later, EVs were isolated from the bone marrow (BM) and were intravenously injected into unirradiated (so-called bystander) animals. EV-induced systemic effects were compared to radiation effects in the directly irradiated animals. Similar to direct radiation, EVs from irradiated mice induced complex DNA damage in EV-recipient animals, manifested in an increased level of chromosomal aberrations and the activation of the DNA damage response. However, while DNA damage after direct irradiation increased with the dose, EV-induced effects peaked at lower doses. A significantly reduced hematopoietic stem cell pool in the BM as well as CD4+and CD8+lymphocyte pool in the spleen was detected in mice injected with EVs isolated from animals irradiated with 2 Gy. These EV-induced alterations were comparable to changes present in the directly irradiated mice. The pool of TLR4-expressing dendritic cells was different in the directly irradiated mice, where it increased after 2 Gy and in the EV-recipient animals, where it strongly decreased in a dose-independent manner. A panel of eight differentially expressed microRNAs (miRNA) was identified in the EVs originating from both low- and high-dose-irradiated mice, with a predicted involvement in pathways related to DNA damage repair, hematopoietic, and immune system regulation, suggesting a direct involvement of these pathways in mediating radiation-induced systemic effects. In conclusion, we proved the role of EVs in transmitting certain radiation effects, identified miRNAs carried by EVs potentially responsible for these effects, and showed that the pattern of changes was often different in the directly irradiated and EV-recipient bystander mice, suggesting different mechanisms.
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Tünde
authors.initials: T
authors.lastname: Szatmári
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Dávid
authors.initials: D
authors.lastname: Kis
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Enikő Noémi
authors.initials: EN
authors.lastname: Bogdándi
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Anett
authors.initials: A
authors.lastname: Benedek
authors.affiliation: Genomic Instability Group, Department of Biological and Medical Sciences, Oxford Brookes University , Oxford , UK.
authors.forename: Scott
authors.initials: S
authors.lastname: Bright
authors.affiliation: Genomic Instability Group, Department of Biological and Medical Sciences, Oxford Brookes University , Oxford , UK.
authors.forename: Deborah
authors.initials: D
authors.lastname: Bowler
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Eszter
authors.initials: E
authors.lastname: Persa
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Enikő
authors.initials: E
authors.lastname: Kis
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Andrea
authors.initials: A
authors.lastname: Balogh
authors.affiliation: Research Group for Molecular Biophysics, Hungarian Academy of Sciences, Semmelweis University , Budapest , Hungary.
authors.forename: Lívia N
authors.initials: LN
authors.lastname: Naszályi
authors.affiliation: Genomic Instability Group, Department of Biological and Medical Sciences, Oxford Brookes University , Oxford , UK.
authors.forename: Munira
authors.initials: M
authors.lastname: Kadhim
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Géza
authors.initials: G
authors.lastname: Sáfrány
authors.affiliation: Division of Radiation Medicine, National Public Health Centre, National Research Directorate for Radiobiology and Radiohygiene , Budapest , Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Lumniczky
keywords: bystander effects; extracellular vesicles; hematopoietic system; ionizing radiation; microRNA