Exploring Functionally Enhanced BLP‐Trained Macrophage Subpopulations in S. Aureus Infection: Underlying Mechanisms and Therapeutic Significance

Abstract Tolerance to bacterial lipoprotein (BLP) is an evolved protective mechanism characterized by an enhanced resistance of BLP‐trained macrophages to microbial infection. However, the underlying mechanisms are not fully understood, and their potential for translational clinical application needs further evaluation. In the present study, through single‐cell RNA sequencing (scRNA‐seq), transcriptomic profiles in both naïve and BLP‐trained bone marrow‐derived macrophages (BMDMs) during Staphylococcus aureus infection are analyzed, and 13 distinct BMDM subpopulations are identified. Notably, BLP‐trained tolerance initiates the emergence of two novel BMDM subpopulations, C5 and C7, characterized by increased antibacterial gene expression and enhanced anti‐inflammatory and antioxidative stress abilities. Moreover, BLP‐trained BMDMs demonstrate activation of the NRF2 signaling pathway, thereby augmenting an antioxidative stress response and mitigating oxidative stress‐induced cell damage and ferroptosis, while undergoing metabolic reprogramming characterized by enhanced glycolysis and oxidative phosphorylation pathways, together with increased anti‐inflammatory metabolites. Critically, in vivo adoptive transfer of BLP‐trained BMDMs protects mice against sepsis‐associated lethality by attenuating systemic inflammatory response, accelerating bacterial clearance, and alleviating organ damage. Collectively, the present study presents a single‐cell atlas of murine BMDMs at rest and under S. aureus infection following BLP training, which reveals novel mechanisms of BLP training‐altered macrophage immunity and identifies macrophage subpopulations responsible for an enhanced resistance to infection, thus offering new preventive and therapeutic strategies for sepsis.