LncRNA ZFPM2 silencing alleviates lung epithelial injury by inducing M2 macrophage polarization: possible implication in bronchopulmonary dysplasia

Background To screen the key long-chain non-coding RNA (LncRNA) closely related to the occurrence and development of Bronchopulmonary dysplasia (BPD), and explore its mechanism of affecting lung epithelial cell injury. Methods Based on the BPD mouse model induced by lipopolysaccharide (LPS), LncRNA high-throughput sequencing was used to screen differentially expressed LncRNAs. GO and KEGG functional enrichment analysis were performed on differentially expressed target genes. The expressions of key LncRNA in LPS-induced MLE-12 and MH-S cells were verified. ZFPM2 specific siRNA (si-ZFPM2) and negative control (si-NC) plasmids were transfected into LPS-induced cells. Cells were divided into control group, LPS group, LPS + si-NC group, and LPS + si-ZFPM2 group. Cell vitality was measured by CCK-8 method, pro-inflammatory cytokines (IL-1β, TNF-α) and anti-inflammatory cytokines (IL-10, IL-4) were quantified, and M1 (iNOS, CD86) and M2 (CD206, Arg1) markers were detected. In MLE-12 cells, cell apoptosis rate was further detected, and the protein expressions of NLRP3 and caspase-1 were analysed. A Transwell co-culture system was established with MH-S cells in the upper chamber (treated as above) and MLE-12 cells in the lower chamber; the latter were harvested to assess viability, apoptosis, NLRP3/caspase-1 expression, and inflammatory cytokine levels. Results A total of 1,290 differentially expressed LncRNAs and 4,084 differentially expressed mRNAs were screened by LncRNA sequencing. Functional enrichment analysis showed that these differential genes were closely related to the development of lung epithelial cells and macrophage polarization. The expression of ZFPM2 was markedly upregulated in BPD mouse lung tissue and in LPS-stimulated cells. In MH-S cells, silencing ZFPM2 significantly increased cell viability, decreased M1 markers (iNOS, CD86) and pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), and increased M2 markers (CD206, Arg1) and anti-inflammatory cytokines (IL-4, IL-10). In MLE-12 cells, silencing ZFPM2 significantly improved viability, reduced apoptosis, and suppressed NLRP3/caspase-1 protein expression and IL-1β, IL-6, and TNF-α levels. In the co-culture system, silencing ZFPM2 significantly enhanced MLE-12 viability, reduced apoptosis and NLRP3/caspase-1 expression, lowered pro-inflammatory cytokines, and elevated anti-inflammatory cytokines. Conclusions Silencing ZFPM2 can alleviate LPS-induced injury of pulmonary epithelial cells, which may be related to promoting the polarization of alveolar macrophages towards M2 type and inhibiting inflammatory response.