Overexpression of Ptpn2 inhibits SiO₂-mediated inflammatory response in alveolar type II epithelial cells

Background Protein tyrosine phosphatase non-receptor type II (PTPN2) is essential for the regulation of inflammation and immunity, but the specific mechanism of action of Ptpn2 in silicosis is unknown.

Objective To investigate the regulatory role of overexpression of Ptpn2 in SiO₂-mediated inflammatory response in alveolar type II epithelial cells based on transcriptome sequencing.

Methods This study was an in vitro study. A negative control group (vector transferred) and an overexpression of Ptpn2 group of mouse lung epithelial cell line MLE-12 cells were firstly constructed. Transcriptome sequencing was performed to detect differentially expressed genes (DEGs), differentially expressed mRNAs, and differentially expressed ncRNAs in the two groups of MLE-12 cells, and then the DEGs were analyzed by the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). Constructed MLE-12 cells and A549 cells were stimulated using SiO₂ suspension, and divided into a negative control group (vector transferred), an overexpression of Ptpn2 group, a negative control + SiO₂ group, and an overexpression of Ptpn2 + SiO₂ group, respectively. Protein expressions of tumor necrosis factor-α (TNF-α) and interleukin (IL)-17A, IL-2, IL-1β were detected by Western blot. Positive TNF-α expression was detected by immunofluorescence staining.

Results The results of Western blot showed that the protein expression level of PTPN2 was up-regulated in the overexpressed Ptpn2 group compared with the negative control group (P < 0.05). The volcano plot and clustering heat map showed that there were 1122 DEGs, 3681 differentially expressed mRNAs, and 474 differentially expressed ncRNAs in the overexpressed Ptpn2 group compared with the negative control group. The results of GO enrichment showed that, in terms of the biological process, the DEGs were mainly related to the regulation of metal ion transport, extracellular matrix organization, and extracellular structural organization; in terms of cellular composition, the DEGs were mainly related to collagen-containing extracellular matrix, receptor complexes, and basement membranes; in terms of molecular function, the DEGs were mainly related to the extracellular matrix structural constituents, glycosaminoglycan binding, and semaphorin receptor binding. The results of KEGG enrichment showed that the DEGs were closely related to cytokin-cytokine receptor interaction, IL-17 signaling pathway, TNF signaling pathway, and chemokine signaling pathway. In MLE-12 and A549 cells, the results of Western blot showed that the protein expression levels of TNF-α , IL-17A, IL-2, and IL-1β were up-regulated in the negative control + SiO₂ group compared with the negative control group (P < 0.05), and the protein expression levels of TNF-α, IL-17A, IL-2, and IL-1β were down-regulated in the overexpression of Ptpn2 + SiO₂ group compared with the negative control + SiO₂ group (P < 0.05). The immunofluorescence staining showed that the expression of TNF-α was increased in the negative control + SiO₂ group compared with the negative control group, and decreased in the overexpression of Ptpn2 + SiO₂ group compared with the negative control + SiO₂ group.

Conclusion Overexpression of Ptpn2 inhibits SiO₂-mediated inflammatory response in MLE-12 cells and A549 cells.