Extracellular release of enzymes from macrophages in vitro for measuring cellular interaction with particulate and non-particulate materials

Cellular effects of an anionic surfactant detected in V79 fibroblasts by different cytotoxicity tests

Several cytotoxicity tests were employed to detect the cellular effects of low concentrations of the anionic surfactant linear alkylbenzene sulphonate (LAS). When added to growth medium containing 5% foetal calf serum, LAS did not affect V79 cell growth, nor did it alter the permeability of cell membranes. The inactivity depended on the serum component of the medium. When treatments were carried out in serum-free saline, LAS inhibited cell proliferation, made the plasma membrane permeable to otherwise-undiffusible compounds, and reduced the uptake of tritiated thymidine. The alterations in membrane permeability were evaluated from the release of cytoplasmic molecules of different size (lactate dehydrogenase, adenine nucleotides, RNA) into the medium. The sensitivity of the spectrophotometric lactate dehydrogenase assay was inadequate for the conditions of treatment required to detect the cytotoxicity of LAS. In cultures pre-incubated with tritiated adenine instead, the release of labelled ATP pool components was time and dose dependent and allowed discrimination between levels of membrane damage causing the same degree of trypan blue staining. Also, macromolecular nucleic acids were detected outside the treated cells at doses of 4-6 mg LAS/litre, which indicated severe membrane damage.

Titanium-induced enzyme activation on murine peritoneal macrophages in primary culture

The biological performance of titanium (Ti) particles has been investigated in vitro on murine peritoneal macrophages in a primary culture system. The ultrastructural study revealed an unchanged morphology with respect to controls and the presence of numerous phagocytic vacuoles containing Ti particles as confirmed by X-ray microprobe analyses. The activities of beta-glucuronidase, acid phosphatase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase were determined. All of the enzymes were found to be activated after different exposure times to various Ti concentrations. These activations are qualified as the consequence of cell defence rather than a significant cytotoxic effect. Nevertheless, they indicate a possible inflammatory action of short duration. This investigation provides new arguments for the high biological performance of Ti.

Loss of cathepsin B activity in alveolar macrophages after in vitro quartz phagocytosis

Bovine alveolar macrophages were incubated up to 20 h with DQ12 quartz particles, either in untreated native form or pretreated with dipalmitoyl lecithin. The content of cathepsin B and N-acetylglucosaminidase was measured in the culture supernatant and in the cells. After incubation, a loss of about 50% of the total cathepsin B activity in the culture dish was observed, whereas no influence on total N-acetylglucosaminidase content occurred. Loss of cathepsin B activity was completely prevented by the pretreatment of quartz with the surfactant component dipalmitoyl lecithin. Similarly, a complete abrogation of the quartz effect on cathepsin B was noted when the cells were incubated with quartz in the presence of NH4Cl in order to prevent phagosome-lysosome fusion. There was also no influence on cathepsin B activity when a lysosome-rich fraction, prepared from alveolar macrophages, was incubated together with quartz. It was concluded that the reduction of cathepsin B activity was related with the intralysosomal deposition of quartz particles.

Cytotoxic effects of quartz and chrysotile asbestos: in vitro interspecies comparison with alveolar macrophages

Cytotoxic effects of DQ12 quartz and chrysotile asbestos on alveolar macrophages of different animal species were compared in vitro. The type of cell reaction toward the cytotoxic dusts was always the same: a loss of cell viability (trypan blue dye exclusion test) was accompanied by the release of cytoplasmic and lysosomal enzymes. The extent of cellular destruction depended upon the amount of dust applied. In the range of 50-100 micrograms/ml quartz or chrysotile asbestos, species-specific variations were observed in the sensitivity of the cells. At this concentration alveolar macrophages of dogs, monkeys, and human patients were damaged to a greater extent than the cells from rats and cattle. Simultaneous incubation of the cells with quartz and L-alpha-dipalmitoyl lecithin resulted in a reduction of the cytotoxic quartz effect. The extent of the protective effect varied according to the species. In the case of chrysotile asbestos no reduction of the fibers cytotoxicity was observed in the presence of L-alpha-dipalmitoyl lecithin.