Background: Particulate air pollution (PM10) consists of a mixture of components, including nanoparticles and metals. Studies from our laboratory have demonstrated that transition metals can potentiate the ability of nanoparticles to induce lung inflammation and that the zinc content of PM10 was largely responsible for their potential to induce inflammation. These results are also relevant to zinc-containing engineered nanoparticles.Objectives: To investigate the potential of ZnCl2 and FeCl3 to interact with nanoparticle carbon black in cell-free and biological systems to generate ROS, express pro-inflammatory mediators and cytotoxic ability. Methods: ROS production was examined using DCFH-DA. J774 cells were treated for 4 h with 14 nm CB and/or ZnCl2 before measuring TNF-alpha. by ELISA. Cytoskeletal changes were investigated using confocal microscopy. Flow cytometry was used to examine apoptotic/necrotic cells and phagocytic ability.Results: In a cell-free system the particles generated significant ROS, whereas ZnCl2 did not. Treatment of cells with 100 mu M ZnCl2, but not FeCl3, increased TNF-alpha. Treatment with 14 nm CB alone induced TNF-alpha, which was synergistically enhanced by ZnCl2. No interactions were observed in cells treated with 14 nm CB and FeCl3. Cytoskeletal changes were observed with increasing concentrations of ZnCl2. These results were confirmed by flow cytometry indicating that ZnCl2 induced markers of apoptosis and necrosis. The phagocytic ability of cells was also significantly decreased. Nanoparticle carbon black alone did not induce changes in apoptosis/necrosis or the phagocytosis activity of the cells.Conclusion: Despite an inability to induce ROS production, ZnCl2 stimulated TNF-alpha production which was synergistically enhanced by 14 nm carbon black. The ability of zinc to induce morphological changes and cell death was not altered by nanoparticle treatment. (c) 2007 Elsevier Inc. All rights reserved.

Both the ultrafine particle and transition metal components of particulate air pollution (PM10) have been hypothesized to be important factors in determining toxicity and potential adverse health effects. In this study we aimed to investigate interactions between transition metal salts and a surrogate environmental particle–ultrafine carbon black (ufCB). In all experimental systems employed, the ufCB was found to be more reactive than its fine counterpart (CB). Incubation of ufCB with the reactive oxygen species (ROS)-sensitive probe dichlorofluorescin in the absence of cells generated significantly more ROS than CB. With addition of either cupric sulfate (CuSO4), ferrous sulfate (FeSO4), or ferric chloride (FeCl3), the ROS generation in the presence of ufCB was enhanced in a potentiative manner. In Mono Mac 6 macrophages, ufCB again produced more ROS than CB. However, addition of iron salts had no additive effect over and above that induced in the macrophages by ufCB. In the mouse macrophage cell line J774, ufCB decreased the cellular content of GSH and ATP. Addition of iron further decreased both GSH and ATP and a potentiative interaction between ufCB and FeSO4 was observed, but only at the highest iron concentrations tested. A concentration-dependent increase in tumor necrosis factor-α production by J774 cells was also observed following exposure to ufCB, which was not further enhanced by the addition of iron. J774 cells were also found to sequester or chelate iron without inducing toxicity. In the rat lung ufCB induced a significant neutrophil influx and this inflammatory effect was potentiativelly enhanced by the addition of FeCl3 (100 μM). These findings suggest that (1) ultrafine particles and metals interact by chemical potentiation in a cell-free environment to generate ROS, (2) potentiation between ultrafine particles and metal salts is not observed in the presence of macrophages as iron is sequestered or chelated by the cells, (3) in the lung, ultrafine particles and iron salts interact in a potentiative manner to generate inflammation.