Comparative in vitro cytotoxicity of nickel oxides and nickel-copper oxides to rat, mouse, and dog pulmonary alveolar macrophages

Respiratory burst in alveolar macrophages exposed to urban particles is not a predictor of cytotoxicity

We examined the utility of respiratory burst measurements in alveolar macrophages to assess adverse cellular changes following exposure to urban particles. Cells were obtained by bronchioalveolar lavage of Fisher 344 rats and exposed (0-100 μg/well) to urban particles (EHC-93, SRM-1648, SRM-1649, PM2.5), the soluble (EHC-93sol) and insoluble (EHC-93insol) fractions of EHC-93 (EHC-93tot), mineral particles (TiO(2), SiO(2)) and metal oxides (iron III oxide, iron II/III oxide, copper II oxide, nickel II oxide). The particle-induced respiratory burst was measured by chemiluminescence for 2h after the addition of particles. The cells were then stimulated with phorbol 12-myristate 13-acetate (PMA), yeast Zymosan fragments (Zymosan), or lipopolysaccharide plus interferon-gamma (LPS/IFN-γ) and the stimulant-induced respiratory burst was measured. Independently of the potential of particles to induce directly a respiratory burst, exposure to most particles attenuated the subsequent stimulant-induced burst. The notable exception was SiO(2), which produced a strong respiratory burst upon contact with the macrophages and enhanced the subsequent response to PMA or LPS/IFN-γ. Based on the degree of inhibition of the stimulant-dependent respiratory burst, particles were clustered into groups of high (SRM-1649, iron III oxide), intermediate (EHC-93tot, EHC-93insol, SRM-1648, VERP, iron II/III oxide, copper II oxide), and low (EHC-93sol, SiO(2), TiO2 and nickel II oxide) potency. Across these clusters, the potency of the particles to inhibit the stimulant-dependent respiratory burst showed poor correlation with cytotoxicity determined by XTT reduction assay.

High content image analysis for human H4 neuroglioma cells exposed to CuO nanoparticles

Background

High content screening (HCS)-based image analysis is becoming an important and widely used research tool. Capitalizing this technology, ample cellular information can be extracted from the high content cellular images. In this study, an automated, reliable and quantitative cellular image analysis system developed in house has been employed to quantify the toxic responses of human H4 neuroglioma cells exposed to metal oxide nanoparticles. This system has been proved to be an essential tool in our study.

Results

The cellular images of H4 neuroglioma cells exposed to different concentrations of CuO nanoparticles were sampled using IN Cell Analyzer 1000. A fully automated cellular image analysis system has been developed to perform the image analysis for cell viability. A multiple adaptive thresholding method was used to classify the pixels of the nuclei image into three classes: bright nuclei, dark nuclei, and background. During the development of our image analysis methodology, we have achieved the followings: (1) The Gaussian filtering with proper scale has been applied to the cellular images for generation of a local intensity maximum inside each nucleus; (2) a novel local intensity maxima detection method based on the gradient vector field has been established; and (3) a statistical model based splitting method was proposed to overcome the under segmentation problem. Computational results indicate that 95.9% nuclei can be detected and segmented correctly by the proposed image analysis system.

Conclusion

The proposed automated image analysis system can effectively segment the images of human H4 neuroglioma cells exposed to CuO nanoparticles. The computational results confirmed our biological finding that human H4 neuroglioma cells had a dose-dependent toxic response to the insult of CuO nanoparticles.

Species differences in the structure and function of the immune system

With the recent publication of regulatory guidelines from both the FDA and the CPMP addressing the investigation of immunotoxicity of new chemical entities has come the requisite increased application of immunotoxicology protocols. Importantly, the fulfillment of these protocols may require the use of different species, and while in many cases information concerning the structure and function of the immune system can be readily translated across species, there are numerous and significant species differences that need to be considered. In some cases, the generation of meaningful immunotoxicology data can be adversely affected by the choice of a species that does not adequately share the immune function of concern with man. Likewise immunotoxicology testing in one species may produce negative data in one species but positive data in another. Knowing the mechanistic basis through an understanding of species differences in the structure and function of the immune system is pivotal to success. This becomes especially true as pharmaceutical companies design and develop highly specific immunomodulatory molecules that demonstrate species-specific pharmacology. This review is an exploration of various species differences in the structure and function of the immune system and an attempt to identify those differences that may be important in the conduct of immunotoxicity tests.

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.

Toxicity to alveolar macrophages in rats following parenteral injection of nickel chloride

Alveolar macrophages collected by pulmonary lavage from male Fischer-344 rats at intervals (1-72 hr) after NiCl2 injection (62-500 mumol/kg, sc) were tested by several techniques. Within 1 to 4 hr, the macrophages showed morphological and biochemical signs of activation (hypertrophy, ruffled plasma membrane, increased cyclic AMP concentration, and markedly diminished 5'-nucleotidase activity, assayed by concanavalin A inhibition). Functional impairment (reduced phagocytic activity) was first seen at 24 hr; lipid peroxidation (increased malondialdehyde concentration) was not detected until 48 hr. Dose- and time-related effects of NiCl2 on 5'-nucleotidase activity, phagocytic activity, malondialdehyde concentration, and nickel content of alveolar macrophages were observed 24 to 72 hr postinjection. Diminished cell viability occurred only at 72 hr after the highest dosage of NiCl2. In alveolar macrophages from 63NiCl2-treated rats, 63Ni was located primarily in the cytoplasm, based upon liquid scintillation counting and autoradiography; fractionations of macrophage cytosol by gel filtration chromatography showed that 63Ni was bound to several high- and low-molecular-weight constituents. This study demonstrates that sc administration of NiCl2 to rats caused nickel uptake into and activation of alveolar macrophages, followed by reduced phagocytic capacity. The alveolar macrophage was a cellular target for nickel toxicity following parenteral exposure to NiCl2.