Most solid materials in nature consist of minerals, they are ubiquitous on the surface of the earth. After inhaled in body, they will trigger pulmonary disease. The pathogenesis of mineral dusts is always in the way of disputing and consummating. Researcher should pay great attention to the adverse effect of mineral dust in nonprofessional environment. The biological action of mineral surface is an important aspect to discover mineral dust interface function and molecular toxicological mechanism. At present, the superfine mineral dust and nanometer suspending dust are the important components of dust environment safety assessment.

AIM: To assess the role of surface free radicals and electromotive voltage of fibrous mineral dusts in rabbit pulmonary alveolar macrophage injuries induced by fibrous mineral dusts. METHODS: Changes in cell death ratio, malandialdehyde (MDA) and cellur electrophoresis ratio, lactate dehydrogenate (LDH)and superoxide dismitase(SOD) activities were determined, the technique of cell culture and Scanning electron Microscopy were used to examine the change of membranous permeability, charge and cellular shape. RESULTS: Fibrous wollastonite and tabulate clinoptilolite, which had no OH-, had no cytotoxicity, while fibrous sepiolite, fibrous palygorskite, fibrous brucite and chrysolite asbestos damaged pulmonary alveolar macrophages in various degrees because of the different OH- levels. All the six fibrous mineral dusts changed the cellular electrophoresis ratio. CONCLUSION: The surface electromotive voltage of fibrous mineral dusts is not an important factor, and the cytotoxicity of them may be related to OH- levels on the mineral dust surface.

In order to study the damage mechanism of mineral dusts on the pulmonary alveolar macrophages (AM), the changes of their death ratio, malandialdthyde (MDA) content and activities of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) were measured. And the technique of cell culture in vitro was used to investigate the cytotoxicity of six mineral dusts (twelve crystal habits) from twelve mineral deposits. The results showed that wollstonite and clinoptilolite had no AM cytotoxicity while other fibrous and grainy mineral dusts could damage pulmonary AM in various degrees. The cytotoxicity of fibrous mineral dusts was greater than that of the grainy ones, and the cytotoxicity of dusts was positively correlated with the active OH- content in dusts, but not necessarily so with its SiO2 content. The high pH values produced by dust was unfavorable for the cells survival and the dusts with a low bio-resistance were safe for cells. The content of variable valence elements in dusts could influence their cytotoxicity and the surface charge of dusts was not a stable factor on their toxicity. It indicates that the shape of mineral dusts is one of the factors affecting cytotoxicity, and that the cytotoxicity of mineral dusts mainly depends on their properties.
Animals ; Cell Death ; drug effects ; Cells, Cultured ; Dust ; Macrophages, Alveolar ; cytology ; drug effects ; enzymology ; Male ; Minerals ; chemistry ; toxicity ; Rabbits ; Toxicity Tests

Background Chrysotile is widely used in construction and industry. Research has shown that it is associated with lung fibrosis in occupational groups, but the involvement of microRNAs (miRNAs) in chrysotile-induced lung fibrosis has been less well studied, and the specific mechanism is still unclear. Objective Using next-generation sequencing technology to analyze the effects of chrysotile exposure on the miRNAs expression profiles of human lung epithelial cells (BEAS-2B cells), to explore the variations of differentially expressed miRNAs and related signaling pathways, and to identify potential targets and molecular mechanisms of chrysotile-induced lung fibrosis. Methods Chrysotile was analyzed with a laser particle size analyzer and an X-ray diffractometer for particle size and physical phase. BEAS-2B cells were exposed to chrysotile for designed time sessions (12, 24, and 48 h) and doses (0, 50, 100, and 200 μg·mL⁻¹). Cell viability was detected with a cell viability assay kit (CCK8); expression levels of Fibronectin, Collagen-Ⅰ, and α-smooth muscle actin (α-SMA) were detected by Western blot after exposure to 200 μg·mL⁻¹ chrysotile for 24 h. Sample correlation and changes in miRNAs expression profiles between the chrysotile-exposed and the control groups were analyzed by next-generation sequencing technology. The target genes of differentially expressed miRNAs were predicted and subjected to Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Results The average particle size of the chrysotile dust sample used in this study was 3.58 μm, and the results of X-ray diffraction analysis confirmed the characteristic peaks of chrysotile. Compared with the control group, the chrysotile gradually inhibited the survival rate of BEAS-2B cells with increasing concentration and exposure time (P<0.01). The survival rates of the 50, 100, and 200 μg·mL⁻¹ chrysotile-exposed cells after 12 h exposure were 83.88%±1.86%, 78.07%±3.97%, and 71.95%±2.99%, respectively; the survival rates after 24 h exposure were 77.41%±1.58%, 69.57%±2.23%, and 62.79%±3.65%, respectively; the survival rates after 48 h exposure were 74.31%±4.93%, 65.84%±2.71%, and 52.74%±6.31%, respectively. The Fibronectin, Collagen-Ⅰ, and α-SMA protein expression levels were elevated in the 200 μg·mL⁻¹ chrysotile-exposed BEAS-2B cells (P <0.05). The results of principal component analysis showed that there were differences in the composition of the samples between the chrysotile exposure group and the control group, and a total of 163 differential miRNAs were screened, of which 79 were up-regulated and 84 were down-regulated. The results of GO analysis showed that the differential miRNAs were mainly associated with biological processes such as regulation of transcription by RNA polymerase II, regulation of DNA templated transcription, cellular differentiation, protein phosphorylation, lipid metabolism, and cell cycle, cellular components such as nucleus, cytomembrane, cytoskeleton, mitochondria, and endoplasmic reticulum, as well as molecular functions such as protein binding, metal ion binding, transferase activity, and DNA binding. The results of KEGG analysis revealed that the differential miRNAs were mainly enriched in cancer pathway, phosphatidylinositol 3-kinase/ protein kinase B (PI3K/AKT) pathway, Ras-associated protein 1 (Rap1) pathway, calcium pathway, cyclic guanosine monophosphate/ protein kinase G (cGMP-PKG) pathway, Hippo pathway, cyclic adenosine monophosphate (cAMP) pathway, and Ras pathway. Conclusion Chrysotile exposure could significantly inhibit BEAS-2B cell survival, elevate the expression of lung fibrosis-associated proteins, and induce differential miRNAs expression, affecting biological processes (such as lipid metabolism, protein phosphorylation, and cell cycle) and cell components (such as mitochondria and endoplasmic reticulum), and interfering with PI3K/AKT pathway, Hippo pathway, cAMP pathway, Rap1 pathway, and Ras pathway.