Exosomal miR-148a-3p from LPS-Activated Macrophages Promotes M1 Polarization and Ferroptosis-Related Characteristics of Recipient Macrophages by Reducing SLC7A11

Background: Gram-negative bacterial infection is a major cause of severe inflammatory disorders and cellular damage, with lipopolysaccharide (LPS) as a key pathogenic trigger. Macrophages are central players in LPS-induced inflammatory cascades, yet the mechanisms by which macrophage-derived exosomes propagate inflammatory signals and cellular injury remain elusive. This study aimed to investigate whether LPS-activated macrophage exosomes drive M1 polarization and ferroptosis-related characteristics in recipient macrophages. Methods: RAW264.7 macrophages were treated with LPS. Exosomes were extracted through ultracentrifugation and their characteristics were determined utilizing Western blot, transmission electron microscopy, and nanoparticle tracking analysis. MicroRNA levels were quantified by droplet digital PCR. The functional effects of exosomes and miR-148a-3p inhibitor on recipient macrophages were evaluated via quantitative real-time PCR, Western blot, enzyme-linked immunosorbent assay, malondialdehyde (MDA) detection and ferrostatin-1 (Fer-1) rescue assay. Dual-luciferase reporter assay validated direct targeting relationships. Results: LPS directly induced M1 polarization and pro-inflammatory cytokine secretion in RAW264.7 cells. Exosomes from LPS-stimulated macrophages were enriched with miR-148a-3p and promoted M1 polarization and ferroptosis-related characteristics in recipient cells. Inhibition of miR-148a-3p and Fer-1 treatment effectively negated the LPS-exosome-mediated effects. Mechanistically, miR-148a-3p directly interacted with and inhibited SLC7A11. Conclusion: Exosomal miR-148a-3p derived from LPS-activated macrophages promotes M1 polarization and ferroptosis-related characteristics in recipient macrophages by reducing SLC7A11. This finding uncovers a novel LPS-induced inflammatory signaling pathway in macrophage–macrophage communication and suggests a potential candidate target for intervention in Gram-negative bacteria–related inflammatory injury. The diagram illustrates the interaction between LPS-activated macrophages and recipient macrophages. On the left, LPS-activated macrophages release exosomes, which are depicted as small particles moving towards the recipient macrophages on the right. The exosomes contain exosomal miR-148a-3p, which binds to SLC7A11 in the recipient macrophages. This binding promotes ferroptosis and M1 polarization, leading to the upregulation of iNOS, TNF-alpha, IL-1beta and IL-6. The diagram shows the processes of upregulated and downregulated expression, indicating the influence of exosomes on gene expression in recipient macrophages.LPS-activated macrophages release exosomes, inducing ferroptosis and M1 polarization in recipients.