Table 1.
In vitro new genotoxicity studies on nickel
| Endpoint | Experimental test system | Test substance | Exposure conditions | Result | Comments | Reference |
|---|---|---|---|---|---|---|
| SSBs (Comet assay) | Primary normal human dermal fibroblasts | NiCl2 (purity: 99.99%) Negative and positive controls: substance not specified | 5,000, 10,000, 25,000 and 50,000 μM 2 h exposure | Increased SSBs only at 50,000 μM (tail moment) Positive | According to protocol by Singh et al. (1988) | Belliardo et al. (2018) |
| SSBs (Comet assay) | Human B lymphoblastoid cell line HMy2.CIR | NiCl2 (purity: not specified) Solvent: not specified Negative control: solvent | 0, 80, 160, 320 and 640 μM 24 or 48 h exposure | Increased SSBs only at 640 μM at 24 h and 48 h (% DNA in the tail) Positive 640 μM: increased ROS levels at 48 h but not at 24 h 160, 320 and 640 μM: increased MDA levels at 24 h and 48 h | According to protocol by Singh et al. (1988) 640 μM: modest inhibition of viability at 24 h 160, 320, 640 μM: inhibition of viability at 48 h | Lou et al. (2013) |
| DSBs (γ‐H2AX by western analysis) | Human Hep G2 (hepatoblastoma) and LS‐174T (colorectal adenocarcinoma) cells | NiCl2 (purity > 95%) Solvent: water Negative control: solvent Positive control: 1 μM benzo[a]pyrene | 100, 250, 500, 750 and 1,000 μM 24‐h exposure | Negative | Dose‐dependent decrease in cell viability (up to 50%) | Kopp et al. (2018) |
| Micronuclei, NPB, and NBUD (cytokinesis‐block micronucleus cytome test) | Immortalised human bronchial epithelial cell line (BEAS‐2B) | Water‐soluble nickel (II) chloride (NiCl2·6H2O) Negative control: untreated cells Positive control: mitomycin C | 1, 5 and 10 μg/mL Exposure: 48 h | The frequency of micronuclei in binucleated cells was significantly higher than for control cells for the two highest concentrations tested NiCl2 increased NPB and NBUD frequencies Positive | NiCl2 showed a significant cytostatic effect and also reduced the mitotic index | Di Bucchianico et al. (2018) |
| Chromosomal aberrations | Immortalised human bronchial epithelial cell line (BEAS‐2B) | Water‐soluble nickel (II) chloride (NiCl2·6H2O) Negative control: untreated cells Positive control: mitomycin C | 1, 5 and 10 μg/mL Exposure: 48 h | NiCl2 significantly increased the rate of chromatid‐type aberrations and induced both inter‐ and intra‐arm exchanges It also induced chromosome‐type aberrations, mainly the formation of dicentric chromosomes as well as endo‐reduplications. Various degrees of aneuploidy such as trisomy, and to a lesser extent monosomy, particularly involving chromosomes 1, 3, 14, 20 and 21 The mitotic index slightly decreased following NiCl2 exposures Positive | Di Bucchianico et al. (2018) | |
| SSBs, (Comet assay) | Immortalised human bronchial epithelial cell line (BEAS‐2B) | Water‐soluble nickel (II) chloride (NiCl2·6H2O) Negative control: untreated cells Positive control: H2O2 | 1, 5 and 10 μg/mL Exposure: 48 h | Modest increases of SSBs compared to control without clear dose response Increased ROS level NiCl2 caused a statistically significant increase in intracellular Ca2+ Positive | Di Bucchianico et al. (2018) | |
| DSB (Neutral Comet assay) | A549 cells: human lung carcinoma BEAS‐2B cells: non‐tumorigenic cells, immortalised cell line derived from normal human bronchial epithelium | Water‐soluble nickel (II) chloride (NiCl2) Negative control: water | A549 cells: 0, 100, 250 and 500 μM BEAS‐2B cells: 0, 100 and 250 μM Exposure : 45 h +/– irradiation (5 Gy IR) Harvesting: 24 h post irradiation | 0 μM NiCl2: no increase in DSB in irradiated cells (repair completed at 24 h) > 100 μM: concentration‐dependent increase in DSB persisting 24 h post‐irradiation in irradiated cells At 250 μM (BEAS‐2B) and 500 μM (A549): small increases in the median comet tail moment were observed in non‐irradiated cells Positive Nickel inhibits repair of IR‐induced DSB in tumorigenic and non‐tumorigenic lung cells | Scanlon et al. (2017) |
DSBs: double‐strand breaks; IR: irradiation; MDA: malondialdehyde; NiCl2: nickel chloride; ROS: reactive oxygen species; SSBs: single‐strand breaks; NPB: nucleoplasmic bridges (a biomarker of DNA misrepair and/or telomere end‐fusions); NBUD: nuclear buds (a biomarker of elimination of amplified DNA and/or DNA repair complexes).