Lianhua Qingwen protects LPS-induced acute lung injury by promoting M2 macrophage infiltration.

Ethnopharmacological Relevance: Traditional Chinese medicine Lianhua Qingwen (LHQW) was used to treat regular seasonal influenza. In recent years, LHQW exerts significant therapeutic effects in treating influenza and Coronavirus Disease 2019 (COVID-19). However, the potential mechanisms are not yet understood and need further study.

Aim Of Study: This study aims to look into the influence of LHQW on lung inflammation and macrophage phenotype, and to clarify the connection between macrophage plasticity and LHQW.

Methods: The cell viability, marker expression, response to LPS stimulation, and phagocytosis of Raw264.7 were detected after LHQW treatment. In an LPS-induced acute lung injury (ALI) mouse model, the alleviating effect of LHQW on lung injury was investigated. The total macrophages and M2 macrophages in mice lungs and the peripheral blood monocytes after LHQW treatment were detected. The cell viability and polarization of peripheral blood macrophages treated with LHQW were detected.

Results: Here, we demonstrate that LHQW protects LPS-induced ALI by promoting M2 macrophage infiltration. LHQW treatment inhibited the inflammatory response and pro-inflammatory phenotype of Raw264.7 macrophages. High concentrations of LHQW promoted the phagocytic capacity of Raw264.7 macrophages. In an ALI mouse model, LHQW alleviated lung injury and no significant hepatotoxicity was observed. By Immunohistochemistry (IHC) analysis, LHQW increased the infiltration of macrophages, mainly M2 macrophages. Consistent with Raw264.7, LHQW also decreased the expression of M1 markers in peripheral blood macrophages. In addition, LHQW blood plasma promoted the M2-type polarization of peripheral blood macrophages.

Conclusions: Taken together, our data demonstrate that LHQW reduces the inflammatory response and ameliorates acute lung injury by promoting anti-inflammatory polarization of macrophages.