Imperatorin inhibits LPS-induced bone marrow-derived macrophages activation by decreased NF-κB p65 phosphorylation.

Background: Imperatorin (IMP) is a secondary metabolite of plants and is the most abundant in Angelica dahurica. Previous studies showed that IMP exhibited anti-inflammatory activity in RAW264.7 cell line. Here, we aim to investigate the roles and mechanisms of IMP in bone marrow-derived macrophages (BMDMs), in view of the difference between primary macrophages and cell lines.

Methods: BMDMs were stimulated with LPS for the inflammation model. Flow cytometry was performed with BMDMs treated with different doses of IMP (0-20mg/L) within staining Annexin V-APC for 5 min. The cytokines and inflammatory mediators were detected by RT-PCR or ELISA. RNA-seq was performed in IMP-treated BMDMs or control, stimulated with LPS for 6h. Western blotting is carried out to determine the phosphorylation of p65, ERK1/2, JNK1, p38, and Akt.

Results: Our results showed that IMP inhibited IL-12p40, IL-6, TNF-α and IL-1β in LPS-stimulated BMDMs. RNA-seq analysis suggested that IMP inhibits Toll-like receptor signaling pathway (KEGG), TNF signaling pathway (KEGG), NF-κB signaling pathway (KEGG), Inflammatory Response (GO). In addition, IMP inhibited myd88, tpl2, cxcl1, ptgs2(COX-2) expression in mRNA level. Finally, we found decreased phosphorylation of NF-κB p65 in IMP-treated BMDMs, after stimulated with LPS.

Conclusion: IMP inhibits IL-12p40, IL-6, TNF-α, and IL-1β expression in LPS-stimulated BMDMs. IMP inhibits macrophage activation, which maybe resulted in decreased phosphorylation of NF-κB p65. Furthermore, IMP may protect against the progress of inflammatory-related diseases.