SAA1 as a key mediator of immune inflammatory pathways in fungal keratitis through FOXO3a phosphorylation regulation

Fungal keratitis (FK) is a severe ocular infection, with its underlying molecular mechanisms remaining incompletely understood. This study aimed to identify and investigate key genes involved in immune-inflammatory responses associated with FK pathogenesis using bioinformatics and in vitro assays.

Transcriptomic data from the Gene Expression Omnibus (GEO) database (GSE58291) were analyzed using the limma package to identify differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to evaluate significant biological processes and pathways related to DEGs. Weighted gene co-expression network analysis (WGCNA) identified gene modules linked with FK-associated DEGs, and Venn diagram analysis highlighted core genes. Receiver operating characteristic (ROC) analysis assessed diagnostic potential. Immune cell composition was analyzed using CIBERSORT, and correlations between key genes and immune cells were evaluated. In vitro, human corneal epithelial cells (HCEC) were stimulated with Aspergillus fumigatus (A.F.), and pro-inflammatory cytokine expression (IL-1β, TNF-α, IL-6) was assessed using enzyme-linked immunosorbent assay (ELISA). Western blot and quantitative real-time polymerase chain reaction (RT-qPCR) analyzed FOXO3a phosphorylation and gene expression changes post-SAA1 siRNA transfection.

A total of 101 DEGs were identified, with WGCNA revealing 6 co-expression network modules, with significant associations noted in yellow and black modules. Nine shared genes were identified in DEGs and modules, with SAA1 strongly linked to FK pathogenesis. SAA1 expression was positively correlated with neutrophils, T cells CD4 memory activated, T cells gamma delta, and activated mast cells. Upon stimulation with A.F., cytokine expression increased, peaking at 24 h. Inhibition of SAA1 reduced FOXO3a phosphorylation and pro-inflammatory cytokine levels, underscoring SAA1's role in FK inflammation via FOXO3a regulation.

SAA1 is a key gene in FK, promoting inflammation by modulating FOXO3a phosphorylation. This highlights its potential as a therapeutic target in managing FK-related inflammation.