Human buccal epithelium cell response to low intensive neutron radiation

Abstract

Background: The investigation of the low doses of ionizing radiation is still a great importance for identification of the threshold of harmful effect and potential hormetic effect of low doses. Objectives: The purpose of investigation was to evaluate the stress response in human buccal epithelium cells induced by low intensive neutron radiation. Materials and Methods: The level of chromatin condensation in interphase nuclei was applied for assessment of the cell reaction to stress. Exfoliated human buccal epithelium cells were collected, placed in the 3.03 mM phosphate buffer solution (pH=7.0) with addition of 2.89 mM CaCl2 and exposed to neutron radiation from 2 Pu-Be sources IBN-17. The heterochromatin granule quantity (HGQ) assessments were done after orcein staining that had been immediately performed after cell exposure to neutron radiation in the dose range from 2.3 mSv to 146.0 mSv. Also the effect of fast neutron radiation in the dose of 11.4 mSv on human buccal epithelium cells was investigated in 1-64 min after exposure. The HGQ in every variant of experiment was assessed in 30 nuclei in 3 separate experiments. The mean HGQ and standard error of mean were assessed in every experiment. Results: Neutron radiation induced the increase of HGQ. Partially slowed neutrons have less influence on neutron-induced HGQ increase than only fast neutrons especially with 1 min delay after exposure. Fast neutrons induce heterochromatinization in cell samples irradiated with doses 4.6–36.5 mSv. Further increase of dose has led to return of HGQ to control levels. After cell exposure to fast neutron flow (11.4 mSv) the peaks of chromatin condensation were observed for time intervals 2–8 and 32–64 min after cell exposure to radiation. Conclusions: Qualitative characteristic of neutron radiation (slow/fast neutrons) influences the rate of cell stress response as revealed by chromatin condensation in cell nuclei. It was demonstrated that there is a threshold dose above which cells are able to develop stress response to neutron radiation. The dose-response dependence is non-monotonous and is of wave-like form. Described phenomena may be explained by the effect of hormesis.