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.