HMGB1 promotes LPS-induced M1 polarization and apoptosis in microglia by mediating the expression of immune and inflammation-related genes

Neuroinflammation is recognized as a core pathogenic mechanism of postoperative cognitive dysfunction (POCD), with microglia hyperactivation and subsequent M1/M2 polarization imbalance identified as critical contributing factors. High-mobility group box 1 (HMGB1), a damage-associated molecular pattern (DAMP), amplifies neuroinflammation; however, whether it mediates POCD through regulating microglia polarization remains unclear. Using BV2 cells as the model, a POCD-like neural injury model was established by lipopolysaccharide (LPS) treatment, followed by HMGB1 knockdown. Cell proliferation and viability under different conditions was measured using the CCK-8 assay. Cell apoptosis was detected by flow cytometry. The expression of microglial polarization marker genes was assessed via RT-qPCR. Inflammatory cytokine levels were quantified by ELISA. Transcriptome sequencing was performed to analyze differentially expressed genes (DEGs) influenced by HMGB1, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Key targets regulated by HMGB1 were identified by integrating immune-related and polarization-related gene sets. HMGB1 knockdown significantly rescued the LPS-induced suppression of BV2 cell proliferation and reduced LPS-triggered apoptosis. Compared to the LPS group, the HMGB1 knockdown group exhibited downregulated expression of M1 markers (CD80, CD86) and pro-inflammatory cytokines (IL-6, TNF-α, IL-1β), alongside upregulated expression of M2 markers (CD163, CD206, Arginase-1). Transcriptomic analysis revealed that HMGB1 knockdown induced significant differential expression in numerous genes. These genes were primarily enriched in immune- and inflammation-related biological processes. Immune-related genes (Bcl3, Fas, Ifnlr1, Il1rl2, Tnfsf14, Vgf) were highly expressed in the LPS group but significantly downregulated after HMGB1 knockdown. Further analysis of polarization-related genes identified 559 significantly altered M1-type and 41 significantly altered M2-type genes. These genes participate in regulating signaling pathways such as type II interferon, NF-kappa B, TNF, and IL-17. Key M1-type genes (Ccl22, Lcn2, Stat5a, Tlr2) were highly expressed in the LPS group and downregulated after HMGB1 knockdown, while key M2-type genes (Cd74, Egr2) were expressed at low levels in the LPS group and upregulated following HMGB1 knockdown. HMGB1 may drive microglia toward a pro-inflammatory M1 phenotype, thereby mediating neuroinflammatory damage in POCD, potentially through activation of STAT, TNF, and IL-17 signaling pathways. Targeting HMGB1 and its downstream genes (e.g., Ccl22, Lcn2, Stat5a, Tlr2, Cd74, Egr2) could provide effective diagnostic and interventional strategies for POCD. • HMGB1 knockdown reverses LPS-induced suppression of BV2 microglial proliferation and reduces apoptosis. • HMGB1 promotes pro-inflammatory M1 polarization by upregulating M1 markers (CD80, CD86) and pro-inflammatory cytokines (IL-6, TNF-α, IL-1β), while suppressing M2 markers (CD163, CD206, Arginase-1). • Transcriptomic analysis identifies HMGB1-regulated immune and inflammation-related genes (e.g., Bcl3, Fas, Ccl22, Lcn2, Stat5a, Tlr2, Cd74, Egr2), enriched in pathways such as TNF, STAT, and IL-17 signaling. • HMGB1 may drive POCD pathogenesis by skewing microglial polarization toward the M1 phenotype via activation of key inflammatory signaling pathways, suggesting HMGB1 as a potential therapeutic target.