Blimp-1 orchestrates macrophage polarization and metabolic homeostasis via purine biosynthesis in sepsis.

Sepsis is a life-threatening condition characterized by a dysregulated immune response to infection, leading to systemic inflammation and organ dysfunction. Macrophage polarization plays a critical role in pathogenesis of sepsis, and the influence of B lymphocyte-induced maturation protein-1 (Blimp-1) on this polarization is an underexplored yet pivotal aspect. This study aimed to elucidate the role of Blimp-1 in macrophage polarization and metabolism during sepsis. Using a murine cecal ligation and puncture model, we observed elevated Blimp-1 expression in M2 macrophages. Knockdown of Blimp-1 by macrophage-targeted adeno-associated virus in this model resulted in decreased survival rates, exacerbated tissue damage, and impaired M2 polarization, underscoring its protective role in sepsis. In vitro studies with bone marrow-derived macrophage (BMDM), RAW264.7, and THP-1 cells further demonstrated Blimp-1 promotes M2 polarization and modulates key metabolic pathways. Metabolomics and dual-luciferase assays revealed Blimp-1 significantly influences purine biosynthesis and the downstream Ornithine cycle, which are essential for M2 macrophage polarization. In vitro studies with BMDM further suggested that the purine biosynthesis and Ornithine cycle metabolic regulation is involved in Blimp-1's effects on M2 macrophage polarization, and mediates Blimp-1's impact on septic mice. Our findings unveil a novel mechanism by which Blimp-1 modulates macrophage polarization through metabolic regulation, presenting potential therapeutic targets for sepsis. This study highlights the significance of Blimp-1 in orchestrating macrophage responses and metabolic adaptations in sepsis, offering valuable insights into its role as a critical regulator of immune and metabolic homeostasis.