TLR-2-mediated metabolic reprogramming participates in polyene phosphatidylcholine-mediated inhibition of M1 macrophage polarization

Abstract

This study aimed to investigate whether the classic hepatoprotective drug polyene phosphatidylcholine (PPC) regulates macrophage polarization and explores the potential role of TLR-2 in this process. In RAW264.7 macrophages and murine bone marrow-derived macrophages (BMDMs) stimulated by lipopolysaccharide (LPS), PPC significantly inhibited the production of IL-6, TNF-α, and the mRNA expression of M1-type macrophage markers. Consistently, PPC reduced the mRNA expression of several key enzymes in the pathways of glycolysis and lipid synthesis while increasing the expression of key enzymes associated with lipid oxidation. Moreover, blocking the glycolytic pathway using 2-deoxy-D-glucose (2-DG) significantly enhanced the anti-inflammatory effect of PPC. However, inhibition of lipid oxidation using GW9662 (an inhibitor of PPAR-γ) and GW6471 (an inhibitor of PPAR-α) abolished the anti-inflammatory effect of PPC. Interestingly, TLR-2 expression in macrophages was significantly downregulated after exposure to PPC. Moreover, pre-activation of TLR-2 hampered the anti-inflammatory effect of PPC. In addition, PPC did not inhibit the secretion of IL-6 and TNF-α in TLR-2^-/- BMDMs that were activated by LPS. This was consistent with the increased expression of M1 markers and glycolytic and lipid synthesis enzymes but decreased lipid oxidation-related enzymes. These results showed that PPC inhibits the differentiation of M1-type macrophages, which was most likely related to TLR-2-mediated metabolic reprogramming.

Keywords: Macrophage polarization; Metabolic reprogramming; Polyene phosphatidylcholine; TLR-2.