Cytotoxicity of nickel oxide particles in rat alveolar macrophages cultured in vitro

Time-course comparison of pulmonary inflammation induced by intratracheal instillation of four different nickel oxide nanoparticles in male Fischer rats

Occupational exposure to nickel oxide (NiO) is an important cause of respiratory tract cancer. Toxicity is known to be associated with the dissociated component, i.e. nickel (II) ions. To address the relationship between physicochemical properties, including solubility in artificial lysosomal fluid, of NiO and time-course changes in the pulmonary response, we conducted an intratracheal instillation study in male Fischer rats using four different well-characterized NiO products, US3352 (NiO A), NovaWireNi01 (NiO B), I small particle (NiO C), and 637130 (NiO D). The NiOs were suspended in purified water and instilled once intratracheally into male F344 rats (12 weeks old) at 0 (vehicle control), 0.67, 2, and 6 mg/kg body weight. The animals were euthanized on days 3, 28, or 91 after instillation, and blood analysis, bronchoalveolar lavage fluid (BALF) testing, and histopathological examination were performed. The most soluble product, NiO B, caused the most severe systemic toxicity, leading to a high mortality rate, but the response was transient and surviving animals recovered. The second-most-soluble material, NiO D, and the third, NiO A, caused evident pulmonary inflammation, and the responses persisted for at least 91 days with collagen proliferation. In contrast, NiO C induced barely detectable inflammation in the BALF examination, and no marked changes were noted on histopathology. These results indicate that the early phase toxic potential of NiO products, but not the persistence of pulmonary inflammation, is associated with their solubility.

Kinetics and dissolution of intratracheally administered nickel oxide nanomaterials in rats

BACKGROUND

The toxicokinetics of nanomaterials are an important factor in toxicity, which may be affected by slow clearance and/or distribution in the body.

METHODS

Four types of nickel oxide (NiO) nanoparticles were single-administered intratracheally to male F344 rats at three doses of 0.67-6.0 mg/kg body weight. The rats were sacrificed under anesthesia and the lung, thoracic lymph nodes, bronchoalveolar lavage fluid, liver, and other organs were sampled for Ni burden measurement 3, 28, and 91 days post-administration; Ni excretion was measured 6 and 24 h after administration. Solubility of NiO nanoparticles was determined using artificial lysosomal fluid, artificial interstitial fluid, hydrogen peroxide solution, pure water, and saline. In addition, macrophage migration to trachea and phagosome-lysosome-fusion rate constants were estimated using pulmonary clearance and dissolution rate constants.

RESULTS

The wire-like NiO nanoparticles were 100% dissolved by 24 h when mixed with artificial lysosomal fluid (dissolution rate coefficient: 0.18/h); spherical NiO nanoparticles were 12% and 35% dissolved after 216 h when mixed with artificial lysosomal fluid (1.4 × 10^-3 and 4.9 × 10^-3/h). The largest irregular-shaped NiO nanoparticles hardly dissolved in any solution, including artificial lysosomal fluid (7.8 × 10^-5/h). Pulmonary clearance rate constants, estimated using a one-compartment model, were much higher for the NiO nanoparticles with a wire-shape (0.069-0.078/day) than for the spherical and irregular-shaped NiO nanoparticles (0-0.012/day). Pulmonary clearance rate constants of the largest irregular-shaped NiO nanoparticles showed an inverse correlation with dose. Translocation of NiO from the lungs to the thoracic lymph nodes increased in a time- and dose-dependent manner for three spherical and irregular-shaped NiO nanoparticles, but not for the wire-like NiO nanoparticles. Thirty-five percent of the wire-like NiO nanoparticles were excreted in the first 24 h after administration; excretion was 0.33-3.6% in that time frame for the spherical and irregular-shaped NiO nanoparticles.

CONCLUSION

These findings suggest that nanomaterial solubility differences can result in variations in their pulmonary clearance. Nanoparticles with moderate lysosomal solubility may induce persistent pulmonary inflammation.

Chromium(III) oxide nanoparticles induced remarkable oxidative stress and apoptosis on culture cells

Chromium(III) oxide (Cr(2)O(3)) is used for industrial applications such as catalysts and pigments. In the classical form, namely the fine particle, Cr(2)O(3) is insoluble and chemically stable. It is classified as a low-toxicity chromium compound. Recently, industrial application of nanoparticles (a new form composed of small particles with a diameter of ≤100 nm, in at least one dimension) has been increasing. Cellular effects induced by Cr(2)O(3) nanoparticles are not known. To shed light upon this, the release of soluble chromium from Cr(2)O(3) nano- and fine-particles in culture medium was compared. Fine Cr(2)O(3) particles were insoluble in the culture medium; on the contrary, Cr(2)O(3) nanoparticles released soluble hexavalent chromium into the culture medium. Cr(2)O(3) nanoparticles showed severe cytotoxicity. The effect of Cr(2)O(3) nanoparticles on cell viability was higher than that of fine particles. Cr(2)O(3) nanoparticles showed cytotoxicity equal to that of hexavalent chromium (K(2)Cr(2)O(7)). Human lung carcinoma A549 cells and human keratinocyte HaCaT cells showed an increase in intracellular reactive oxygen species (ROS) level and activation of antioxidant defense systems on exposure to Cr(2)O(3) nanoparticles. Exposure of Cr(2)O(3) nanoparticles led to caspase-3 activation, showing that the decrease in cell viability by exposure to Cr(2)O(3) nanoparticles was caused by apoptosis. Cellular responses were stronger in the Cr(2)O(3) nanoparticles-exposed cells than in fine Cr(2)O(3) - and CrCl(3) -exposed cells. Cellular uptake of Cr(2)O(3) particles were observed in nano- and fine-particles. The cellular influence of the extracellular soluble trivalent chromium was lower than that of Cr(2)O(3) nanoparticles. Cr(2)O(3) nanoparticles showed cytotoxicity by hexavalent chromium released at outside and inside of cells. The cellular influences of Cr(2)O(3) nanoparticles matched those of hexavalent chromium. In conclusion, Cr(2)O(3) nanoparticles have a high cytotoxic potential.

Cytotoxicity and apoptotic effects of nickel oxide nanoparticles in cultured HeLa cells

The aim of this study was to observe the cytotoxicity and apoptotic effects of nickel oxide nanoparticles on human cervix epithelioid carcinoma cell line (HeLa). Nickel oxide precursors were synthesized by an nickel sulphate-excess urea reaction in boiling aqueous solution. The synthesized NiO nanoparticles (<200 nm) were investigated by X-ray diffraction analysis and transmission electron microscopy techniques. For cytotoxicity experiments, HeLa cells were incubated in 50-500 μg/mL NiO for 2, 6, 12 and 16 hours. The viable cells were counted with a haemacytometer using light microscopy. The cytotoxicity was observed low in 50-200 μg/mL concentration for 16 h, but high in 400-500 μg/mL concentration for 2-6 h. HeLa cells' cytoplasm membrane was lysed and detached from the well surface in 400 μg/mL concentration NiO nanoparticles. Double staining and M30 immunostaining were performed to quantify the number of apoptotic cells in culture on the basis of apoptotic cell nuclei scores. The apoptotic effect was observed 20% for 16 h incubation.

Ultrafine NiO particles induce cytotoxicity in vitro by cellular uptake and subsequent Ni(II) release

Nickel oxide (NiO) is one of the important industrial materials used in electronic substrates and for ceramic engineering. Advancements in industrial technology have enabled the manufacture of ultrafine NiO particles. On the other hand, it is well-known that nickel compounds exert toxic effects. The toxicity of nickel compounds is mainly caused by nickel ions (Ni(2+)). However, the ion release properties of ultrafine NiO particles are still unclear. In the present study, the influences of ultrafine NiO particles on cell viability were examined in vitro to obtain fundamental data for the biological effects of ultrafine green NiO and ultrafine black NiO. Ultrafine NiO particles showed higher cytotoxicities toward human keratinocyte HaCaT cells and human lung carcinoma A549 cells than fine NiO particles and also showed higher solubilities in culture medium (Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum) than fine NiO particles. In particular, the concentration of Ni(2+) released into the culture medium by ultrafine green NiO was 150-fold higher than that released by fine green NiO. The concentrations of Ni(2+) released by both types of NiO particles in an aqueous solution containing amino acids were remarkably higher than those released by NiO particles in water. Moreover, we prepared a uniform and stable dispersion of ultrafine black NiO in culture medium and examined its influence on cell viability in comparison with that of NiCl(2), a soluble nickel compound. A medium exchange after 6 h of exposure resulted in a loss of cytotoxicity in the cells exposed to NiCl(2), whereas cytotoxicity was retained in the cells exposed to NiO. Transmission electron microscope observations revealed uptake of both ultrafine and fine NiO particles into HaCaT cells. Taken together, the present results suggest that the intracellular Ni(2+) release could be an important factor that determines the cytotoxicity of NiO. Ultrafine NiO is more cytotoxic than fine NiO in vitro.

Physicochemical characteristics and toxicity of nickel oxide particles calcined at different temperatures

The physicochemical characteristics and cytotoxicity of two types of commercial nickel oxide particles (black and green nickel oxide) and five types of nickel oxide particles prepared by calcination of the black nickel oxide at 600-1000 degrees C were studied. Thermal analysis with mass spectroscopy showed that the black nickel oxide particles contained approximately 1.4% impurity, which seemed to be basic nickel carbonate. The calcination treatment at 600 degrees C increased the nickel content and decreased the oxygen content, but these remained constant in the particles treated at higher temperatures (700-1000 degrees C) and in the green nickel oxide particles. The water solubility of black nickel oxide particles was markedly greater than that of the other particles, especially in the first 24 h after mixing with water. The solubility of the calcined particles decreased with increasing calcination temperature. The cytotoxicity of these particles was evaluated by the viability of rat alveolar macrophages and by the inhibition of cell proliferation in Chinese hamster ovary cells. The black nickel oxide was the most cytotoxic of the particles examined, and this may be attributable, at least in part, to a rapid dissolution of nickel from the contained impurity. The toxicity of the calcined particles decreased with increasing calcination temperature. These results indicate that water solubility, which depends on calcination temperature, modulates the acute cytotoxicity of nickel oxide particles.

Effects of nickel oxide on the production of tumor necrosis factor by alveolar macrophages of rats

To evaluate the effect of green nickel oxide (NiO) on the production of tumor necrosis factor (TNF) by alveolar macrophages, alveolar macrophages were exposed to NiO in vitro and in vivo. For the in vitro study, rats alveolar macrophages were incubated with NiO on a microplate for 24 h. TNF activity in the culture supernatant was determined by the L929 bioassay. Rats alveolar macrophages cultured with 100 and 200 micrograms/mL of NiO in vitro induced the production of TNF, however, it was not statistically significant compared with the control that was free from NiO exposure. For exposure in vivo, rats were divided into two groups. Five were exposed to a daily concentration of 11.7 +/- 2.0 mg/m3 of NiO for an 8-hr/d, 5 d/wk, for 4 wk, and five rats (control) were kept in a cage and not exposed to NiO. Bronchoalveolar lavage was performed and the recovered alveolar macrophages were incubated on a microplate for 24 h. TNF production by exposed alveolar macrophages was significantly higher than that of controls.