Background Silicosis is caused by long-term inhalation of large amounts of free silica (SiO₂) particles, and exploring its mechanism can provide new directions for the treatment of silicosis fibrosis. Objective To investigate the expression and role of fatty acid binding protein 5 (FABP5) in a silica-induced silicosis model. Methods In combination with the results of single-cell transcriptome sequencing, the expression pattern of FABP5 in mouse alveolar epithelial cells was explored by bioinformatic analysis, and the distribution pattern of fabp5 was detected by spatial transcriptomics. An in vivo model of silicosis was established by intratracheal injection with SiO₂ into mice and four groups were set up: normal saline (NS) 7 d group, NS 56 d group, SiO₂ 7 d group, and SiO₂ 56 d group. An in vitro model of silicosis was established in SiO₂-treated mouse lung epithelial cell line (MLE-12). At the whole animal level, the marker of epithelial cells (E-Cad) and the protein level of FABP5 were detected by tissue immunofluorescence assay; in vitro, the changes of fabp5 mRNA expression and protein level in MLE-12. Results The results of single-cell transcriptome sequencing and spatial transcriptome sequencing showed that the mRNA expression of fabp5 was upregulated in type II alveolar epithelial cells in the focal area of silicosis in mice, accompanied by elevated tissue immunofluorescent protein levels, and there was co-localization of E-CAD. Meanwhile, SiO₂ stimulation induced a 1.58-fold increase in fabp5 mRNA expression and a 2-fold increase in protein levels in MLE-12 cells, with significant differences (P<0.05). Conclusion The protein level of FABP5 is increased in alveolar epithelial cells in a pulmonary fibrosis model, suggesting that FABP5 may be involved in the pathological process of epithelial cells in pulmonary fibrosis.

Silicosis, one of the most serious occupational diseases in the world, is a complex pathological process with multi-cell involvement and multi-factor regulation, and its pathogenesis has not been fully elucidated.Protein phosphatase 2A (PP2A) regulates tumor signaling pathways, cell development and cell cycle.The regulatory subunit B of PP2A binds to the core enzyme, resulting in tissue expression specificity and substrate specificity of the PP2A holoenzyme complex.Protein phosphatase 2A regulatory subunit B"α (PPP2R3A) is a subunit of PP2A regulatory subunit B", which is a regulator of cell proliferation.However, the role of PPP2R3A in pulmonary fibrosis is still unclear.In this study, the pulmonary fibrosis model was established by endotracheal infusion of silica (SiO2, 250 mg/kg).Human pulmonary fibroblast-adult cells (HFP-a) were stimulated with 5 ng/mL TGF-β1 to construct fibro-related cell models.The transcription level of Ppp2r3a was detected by qRT-PCR assay.Immunofluorescence and Western blot experiments were performed to detect protein levels.Cell viability was detected by CCK-8 assay.The cell migration ability was detected by scratch test.Experimental results showed that silica nodules and collagen deposition were obvious in the SiO2 group, and the expression of PPP2R3A in lung fibroblasts increased, which could affect cell viability and migration ability, and may promote the progression of pulmonary fibrosis by regulating the expression of p53 signaling pathways.This study provides a new idea for the prevention and treatment of pulmonary fibrosis.