Features of cellular effects under combined effects of nickel ions and ionizing radiation

Under current conditions the probability of simultaneous effects of radiation and chemical factors on biological objects increases, and that's why the issue of combined influence of factore different by their nature becomes progressively important. The objective was to study the cytotoxicity of nickel ions in a test-system of cell culture and to detect the cellular reactions under a combined impact of nickel ions and ionizing radiation.

Studies were performed on inoculated cell culture line L929. Cells were cultivated according to standard methods of treating the cell strains. After 24 h cultivation the cells were γ-irradiated at the unit "Teratron" (Canada) at doses of 0.5, 5.0 and 10.0 Gy. The water-soluble salt of nickel acetate was added to the culture medium 1 h prior to irradiation in the final concentration of 10, 1, 0.1, or 0.01 μmol/L. Morfological and functional characteristics of cells in a culture were determined at different periods of cultivation. Proliferative cell activity was assessed by growth kinetics: the total number of cells, the number of mitoses and giant multi (2 or more nuclei) cells were counted within grid area of 0.05 mm2. Simultaneously the number of apoptotic cells was determined.

As a result , it was found that nickel ions exhibit the cytotoxic effects on cells in vitro: an increase in concentration of the element caused the cell death intencification with proliferative and mitotic activity decrease. Moreover, at low concentrations (0.01-0.1 μmol/L) the number of atypical polykaryocytes increased as well as the level of apoptosis. When nickel ions concentration increased the cell death took place through apoptosis and necrosis. Under the combined influence of radiation and nickel ions the nonlinear cellular responses were observed: under the low-dose radiation (0.5 Gy) a sensitization of cells to radiation was noted, and the sublethal doses (10 Gy) caused a particular radioprotection. Number of apoptotic cells under these conditions was significantly higher vs. control.

Studies have shown that nickel ions have significant toxic effects on proliferation and mitotic activity of cells in vitro. Under the combined effects of ionizing radiation the cell sensitization to nickel ion was detected till following exposure to low dose (0.5 Gy) and reduction of cells tolerance to sublethal doses of irradiation (10 Gy).