Medulla Tetrapanacis water extract alleviates inflammation and infection by regulating macrophage polarization through MAPK signaling pathway.

Medulla Tetrapanacis (MT) is a commonly used herb to promote lactation and manage mastitis in lactating mothers. However, its anti-inflammatory and anti-bacterial effects are currently unknown. We hypothesized that MT water extract possesses anti-inflammatory and anti-bacterial effects by modulating macrophage polarization to reduce the release of inflammatory mediators and phagocytosis via inactivation of MAPKs pathways. The chemical composition of the MT water extract was analyzed by UPLC-Orbitrap-mass spectrometry. The anti-inflammatory and anti-bacterial properties of the MT water extract were examined using LPS-stimulated inflammation and Staphylococcus aureus infection model in RAW 264.7 cells, respectively. The underlying mechanism of action of the MT water extract was also investigated. We identified eight compounds by UPLC-Orbitrap-mass spectrometry that are abundant within the MT water extract. MT water extract significantly suppressed LPS-induced nitric oxide, TNF-α and IL-6 secretion in RAW 264.7 cells which was accompanied by the promotion of macrophage polarization from pro-inflammatory towards anti-inflammatory phenotypes. MT water extract significantly suppressed the LPS-induced MAPK activation. Finally, MT water extract decreased the phagocytic capacity of the RAW 264.7 cells against S. aureus infection. MT water extract could suppress LPS-induced inflammation by promoting macrophages towards an anti-inflammatory phenotype. In addition, MT also inhibited the growth of S. aureus.