The macrophage induces sepsis-associated lung injury through pyroptosis via the BATF/PLAC8/MAPK pathway in CLP mice

Although Placenta-associated protein 8 (PLAC8) is associated with multiple inflammatory diseases, its role in regulating sepsis-associated lung injury (SALI) remains unexplored. This study aimed to identify the role of PLAC8 in the pathogenesis of SALI and recognize as a correlated biomarker with potential diagnostic value of SALI. The key dysregulated genes were identified, and a sepsis diagnostic model was constructed through Bioinformatics analysis of public sepsis transcriptomic datasets. Then, PLAC8 was knocked down using adeno-associated virus serotype 9 (AAV9) vector in vivo, and changes in SALI symptoms in mice were analyzed. In vitro, phorbol 12-myristate 13-acetate (PMA)-treated THP-1 cells were first transfected with siRNA specific to PLAC8 or Basic leucine zipper ATF-like transcription factor (BATF) or with an overexpression plasmid or treated with the mitogen-activated protein kinase (MAPK) signaling pathway inhibitor (E)-Osmundacetone (Osm) and were then treated with lipopolysaccharide (LPS) + nigericin (Nig) to induce pyroptosis. Immunofluorescence staining, Western blotting, and quantitative reverse transcription polymerase chain reaction were performed to evaluate inflammation and pyroptosis. Based on transcriptomic data, a sepsis diagnostic model containing PLAC8 was constructed with good diagnostic performance. The expression of PLAC8 was consistently upregulated in all sepsis datasets. In vivo, knockdown of PLAC8 could alleviate lung injury, reduce lung inflammation and oxidative stress, and suppresse pyroptosis in septic mice. In vitro, PLAC8 silencing may inhibit macrophage pyroptosis and the release of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and Interleukin-1β (IL-1β). The transcription factor BATF, which was also upregulated in lung tissues of septic mice, was found to transcriptionally activate PLAC8 expression. Functionally, PLAC8 promoted macrophage pyroptosis by activating the MAPK/NOD-like receptor thermal protein domain associated protein 3 (NLRP3)/Gasdermin D (GSDMD) pathway. The pro-pyroptotic effect of PLAC8 overexpression was reversed by either BATF knockdown or MAPK pathway inhibition. BATF, as an upstream regulator of PLAC8, promotes PLAC8 upregulation, which activates the MAPK signaling pathway, thereby exacerbating macrophage pyroptosis and the inflammatory response. PLAC8 represents a correlated biomarker with potential diagnostic value and potential therapeutic target for SALI.