Magnetometric evaluation of the effects of man-made mineral fibers on the function of macrophages using the macrophage cell line RAW 264.7

Man-made mineral fiber effects on the expression of anti-oncogenes P53 and P16 and oncogenes C-JUN and C-FOS in the lung tissue of Wistar rats

Man-made mineral fibers (MMMFs) are substitutes for asbestos. MMMFs are widely used as insulation, but their molecular mechanisms underlying the tumorigenic effects in vivo have been poorly studied. For this reason, this work aimed to explore the properties and carcinogenic molecular mechanisms of MMMFs. The three MMMFs, rock wool (RW), glass fibers (GFs), and ceramic fibers (CFs), were prepared into respirable dust. Particle size, morphology, and chemical composition were analyzed by laser particle analyzer, scanning electron microscope, and X-ray fluorescence spectrometer, respectively. The Wistar rats were administered multiple intratracheal instillations of three MMMFs once a month. Then, several parameters (e.g. body mass, lung mass, and lung histology) were measured at 1, 3, and 6 months. After that, levels of P53, P16, C-JUN, and C-FOS mRNA and protein were measured by quantitative real-time reverse transcription polymerase chain reaction and Western blotting. This work found that exposure to MMMFs could influence the growth of body mass and increase lung mass. General conditions showed white nodules and irregular atrophy. In addition, MMMFs could lead to inactivation of anti-oncogene P16 and activation of proto-oncogenes (C-JUN and C-FOS) in the mRNA and protein levels, in which GF and CF were more obvious compared with RW. The effect of MMMFs was different, which may be related to the physical and chemical characteristics of different MMMFs. In conclusion, MMMFs (GF and CF) could induce an unbalanced expression of cancer-related genes in the lung tissues of rats. The understanding of the determinants of toxicity and carcinogenicity provides a scientific basis for developing and introducing new safer MMMF products, and the present study provides some useful insights into the carcinogenic mechanism of MMMFs.

Evaluation of hazardousness of refractory fibers by cell magnetometry

This study was carried out to assess the cytotoxicity of three kinds of refractory fibers (RFs), RF1, RF2, and RF3, by cell magnetometry, lactate dehydrogenase (LDH) assay and morphological observation by scanning electron microscopy, using a mouse-derived cultured cell line, RAW264.7. As an indicator for cell magnetometry, Fe(3)O(4) was added to RAW264.7 cells. RF1, RF2 and RF3 were each added to an aliquot of this solution to make final concentrations of 250, 500 and 1,000 µg/ml in the experimental group. Phosphate buffered solution was added to make the control solution (n = 6). After culturing for 48 hr, the solution was magnetized from outside using a cell magnetometric apparatus, and the remnant magnetic field was measured for 20 min postmagnetization. In cell magnetometry, a significant delay of relaxation compared to that of the control was observed. In the LDH assay, LDH release into the culture medium was observed by addition of RFs. Furthermore, a quantity-dependent relationship was found between the quantity of RF added and the cytotoxicity in cell magnetometry and LDH assay. Morphological examination revealed incomplete phagocytosis of fibers and a decrease of microvilli in the experimental groups. These results suggest that RFs are cytotoxic to RAW264.7 cells, showing concentration-dependent cytotoxicity, and have a possible risk of cytotoxicity similar to that of asbestos. Further studies by pulmonary magnetometry are necessary to assess the hazardousness of RFs.

Magnetometric evaluation of toxicities of chemicals to the lungs and cells

Because the lungs are exposed to airborne hazardous materials, alveolar macrophages (AMs) play a major role in defending against the exposure to various noxious chemical substances. In this study, we reviewed magnetometric investigations of the effects of various chemicals on the lungs and AMs. Magnetometry, using magnetite as an indicator, was used to evaluate the effects of certain chemicals on the lung and AMs. A rapid decrease of the remanent magnetic field after the cessation of external magnetization, a phenomenon called relaxation, was impaired when the lungs and macrophages were exposed to toxic substances. The delayed in vivo relaxation observed in the lungs exposed to magnetite and gallium arsenide was almost identical to the in vitro relaxation observed in the AMs exposed to the same materials. Delayed relaxation was observed in the AMs exposed to silica dust; various fibers, such as chrysotile and some man-made mineral fibers; and toxic arsenic and cadmium compounds. The extracellular release of lactate dehydrogenase activity was found in the AMs exposed to the chemicals. Relaxation is attributed to the cytoskeleton-driven rotation of phagosomes containing magnetite. While the exact mechanism of delayed relaxation due to exposure to harmful chemicals remains to be clarified, cell magnetometry appears to be useful for the safety screening of chemical substances.