Changes in Nitric Oxide and Superoxide Levels in Human Endotheliocytes and Carcinoma Cells after Exposure to Low-Dose Ionizing Radiation

Abstract

The exposure of HeLa G63 and ECV-304 cells to γ-rays of (137)Cs as well as β-particles of (3)H(2)O and (3)H-thymidine induced changes in redox status of not only irradiated cells, but also their progeny. Increased intracellular levels of nitric oxide (NO) were observed only in HeLa G63 cells and persisted over three cell generations; β-particles from (3)H(2)O were most efficient. Intracellular superoxide (O(2)(-)) level had similar dynamics in both cell lines. Intracellular O(2)(-) level decreased immediately after irradiation, but then increased and significantly surpassed the control level. These changes in the intracellular level of O(2)(-) were accompanied by decondensation of nuclear chromatin. Increased level of free radicals in the progeny of irradiated cells and changes in chromatin conformation and the absence of correlation between radiation-induced structural damage to chromosomes and intracellular level of free radicals suggest participation of epigenetic mechanisms of inheritance.