Luteolin modulates liver macrophage subtype polarization and play protective role in sepsis induced acute hepatic injury.

Background: Luteolin has an anti-inflammatory effect, but the mechanism has not been elucidated in sepsis-induced acute hepatic injury (AHI). The purpose of this study was to investigate the effects and potential mechanisms of luteolin on sepsis-induced AHI.

Methods: In this study, we utilized both wild-type (WT) mice and Toll-like receptor 4 (TLR4)-deficient (TLR4) mice alongside RAW264.7 cells. We constructed a CLP-induced AHI mouse model to study the effects of luteolin on liver inflammation, survival and liver macrophage subtypes in mice. In addition, we extracted mouse serum, mouse bone marrow-derived macrophages (BMDMs) and liver tissue and analysed the effects of luteolin on macrophage polarization subtypes and downstream inflammatory cytokines by flow cytometry, ELISA, Western blotting (WB) and qPCR. To further verify the effect of luteolin on macrophage polarization and explore the possible potential mechanism, we used a CLP-induced AHI mouse model and LPS-stimulated RAW 264.7 macrophages to assess the effect of luteolin on macrophage polarization; the expression of TNF-α and IL-10 in the cell culture supernatant; and the expression of iNOS, ARG-1, NF-κB (P65), p-P65 and MyD88 by flow cytometry, ELISA, immunohistochemistry and Western blotting.

Results: We found that luteolin reduced liver injury and inflammatory response and improved the survival rate of mice. Luteolin modulated the macrophage subtype proportion, promoted the change of macrophages from a proinflammatory M1 phenotype to an anti-inflammatory M2 phenotype, and reduced the inflammatory response both in vivo and in vitro. Moreover, luteolin reduced the expression of NF-κB (p-P65), TLR4 and MyD88. By integrating the predictions from network pharmacology with the in vitro and in vivo experimental results, it was determined that the mechanism by which luteolin alleviates sepsis-induced acute hepatic injury is closely related to the TLR4/MyD88/NF-κB pathway.

Conclusions: The results of this study suggest that luteolin helps alleviate liver injury, reduces the expression of proinflammatory cytokines and promotes the expression of anti-inflammatory factors in sepsis-induced acute hepatic injury. This effect may be related to the regulation of macrophage polarization by luteolin through the TLR4/MyD88/NF-κB signalling pathway.