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This research investigates the radiobiological response and dose-dependent chromosomal damage in human lymphocytes exposed to very high-energy electron (VHEE) beams, employing the cytokinesis-block micronucleus (CBMN) assay—an internationally recognized biodosimetric method endorsed by the International Atomic Energy Agency (IAEA). Micronuclei (MN) are small, extranuclear bodies that form when whole chromosomes or chromosomal fragments are not incorporated during mitosis. The presence of radiation-induced MN, typically assessed in blood lymphocytes, serves as an indicator of unrepaired or misrepaired DNA double-strand breaks. Human peripheral blood is an ideal non-invasive biological sample for cytogenetic tests aimed at detecting DNA damage following irradiation. T-lymphocytes, known for their heightened sensitivity to radiation, are particularly beneficial for studying induced chromosomal damage. These cells are irradiated while synchronized in the G0 phase of the cell cycle, a resting state prior to replication. Following stimulation with phytohemagglutinin (PHA), a mitogenic agent, T-lymphocytes enter mitosis, enabling us to assess the effects of radiation on these cells.
Furthermore, we investigated the impact of VHEE on telomere length and mitochondrial DNA. Telomeres are considered "hallmarks of radiosensitivity" and are primary targets for reactive oxygen species (ROS), which contribute to their progressive shortening and subsequent genomic instability. Mitochondrial DNA (mtDNA) is also vulnerable to ionizing radiation and is more susceptible to damage than nuclear DNA due to the absence of protective histones and limited DNA repair capacity.
Our preliminary findings indicate a radiation dose-response relationship in chromosomal damage, evidenced by an increase in the frequency of MN with higher radiation doses. This phenomenon applies to both targeted effects, where damage occurs in irradiated cells, and indirect effects, characterized by biological changes in non-irradiated cells as a result of signals from irradiated cells. Additionally, we observed radiation-induced telomere shortening due to VHEE exposure; however, no significant difference was found in the analysis of mtDNA copy number (mtDNAcn), a surrogate marker of mitochondrial dysfunction.
