Interactions of alpha Ni3S2 with guinea pig alveolar macrophages and liberation of inflammatory mediators

A pharmacokinetic model of the intracellular dosimetry of inhaled nickel

The potential associations between exposure to nickel compounds and cancer have been evaluated in both animal and epidemiological studies of occupationally exposed workers. The results of the epidemiological studies suggest that not all nickel compounds are equally carcinogenic, an observation supported by the animal bioassay results. Given the complexity and the differences in the modes of uptake of different forms of nickel by cells and the subsequent delivery of nickel to the nucleus, it would be expected that some forms of nickel would be more potent than others. A physiologically based pharmacokinetic (PBPK) model would be useful in estimating the cellular exposure to nickel resulting from inhalation of the different forms of nickel. To this end, a preliminary model of a tracheobronchial epithelial cell was developed to describe the differences in the extracellular and intracellular kinetics of the different classes of nickel compounds. Data available in the published literature were used to define the initial model parameters. The resulting cellular dosimetry model was able to describe kinetic data on three forms of nickel (soluble chloride and insoluble sulfide and subsulfide). This preliminary model development effort has identified critical data gaps that could be filled by additional research. The ultimate goal will be to integrate a refined cellular dosimetry model with published lung deposition/clearance and systemic distribution/clearance models for nickel. The use of such an integrated PBPK model would allow for more biologically based risk estimates for the inhalation of the different nickel compounds, as well as mixtures of these compounds.

Oxidative stress due to nickel toxicity in the liver of protein-deficient rats

This study was designed to determine the oxidative stress induced by nickel sulfate in the liver in the protein-deficient rats. Nickel sulfate in the dose of 800 mg/L in drinking water was administrated to Sprauge Dawley (SD) rats as well as protein-deficient rats for a total duration of 8 weeks. The effects of nickel treatment and protein deficiency separately and in combination were studied on rat liver antioxidant defense system enzymes like catalase, glutathione peroxidase (GPX), glutathione reductase (GR), superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione-S-transferase (GST), as well as on lipid peroxidation (LPO). The investigations revealed a significant increase in the activity of enzymes, which include catalase, Gpx, GR and GST, and in the levels with LPO following nickel treatment in combination with protein deficiency. On the contrary, feeding to control rats resulted in a significant depression in the levels of SOD and GSH. However, nickel treatment to normal rats caused a significant increase in the activity of enzymes catalase and GST and in the levels of LPO, whereas the levels of GSH get significantly depressed. Further, nickel treatment to protein-deficient rats did not cause any additional alteration in the status of liver antioxidants as were observed in conditions of protein deficiency.

Ni2+ enhances Fe2+/peroxide-induced oxidation of arachidonic acid and formation of geno/cytotoxic 4-hydroxynonenal: a possible contributory mechanism in nickel toxicity and allergenicity

Ni(2+), a toxic, carcinogenic and allergenic agent, affected both the kinetic and chemical courses of the Fe(2+)-induced oxidation of arachidonic acid (AA) in 0.05 M phosphate buffer (pH 7.4) and at 37 degrees C. At 10 microM concentration, Ni(2+) decreased the rate of oxidation of peroxide-free AA (200 microM) promoted by 50 microM Fe(2+), as determined by measurement of thiobarbituric acid reactive species (TBARS) and 1H NMR analysis. However, in the presence of low levels of peroxides (e.g. 2%), Ni(2+) exerted a significant stimulatory effect on Fe(2+)-induced AA oxidation and TBARS formation. 1H NMR analysis showed that Ni(2+) (10 microM) enhanced formation of genotoxic alkenals including 4-hydroxy-2-nonenal (4-HNE, GC/MS evidence) by Fe(2+)-promoted degradation of both AA and 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) methyl esters. The observed stimulatory effects of Ni(2+) on peroxide breakdown and cytotoxic aldehyde formation provide an attractive explanation to the enhanced sensitization capacity of nickel in inflammatory states compared to normal states.