Paeoniflorin Coordinates Macrophage Polarization and Mitigates Liver Inflammation and Fibrogenesis by Targeting the NF-?B/HIF-1a Pathway in CCl4-Induced Liver Fibrosis

Liver fibrosis is a disease largely driven by resident and recruited macrophages. The phenotypic switch of hepatic macrophages can be achieved by chemo-attractants and cytokines. During a screening of plants traditionally used to treat liver diseases in China, paeoniflorin was identified as a potential drug that affects the polarization of macrophages. The aim of this study was to evaluate the therapeutic effects of paeoniflorin in an animal model of liver fibrosis and explore its underlying mechanisms. Liver fibrosis was induced in Wistar rats via an intraperitoneal injection of CCl4. In addition, the RAW264.7 macrophages were cultured in the presence of CoCl2 to simulate a hypoxic microenvironment of fibrotic livers in vitro. The modeled rats were treated daily with either paeoniflorin (100, 150, and 200mg/kg) or YC-1 (2mg/kg) for 8 weeks. Hepatic function, inflammation and fibrosis, activation of hepatic stellate cells (HSC), and extracellular matrix (ECM) deposition were assessed in the in vivo and in vitro models. The expression levels of M1 and M2 macrophage markers and the NF-?B/HIF-1a pathway factors were measured using standard assays. Paeoniflorin significantly alleviated hepatic inflammation and fibrosis, as well as hepatocyte necrosis in the CCl4-induced fibrosis model. Furthermore, paeoniflorin also inhibited HSC activation and reduced ECM deposition both in vivo and in vitro. Mechanistically, paeoniflorin restrained M1 macrophage polarization and induced M2 polarization in the fibrotic liver tissues as well as in the RAW264.7 cells grown under hypoxic conditions by inactivating the NF-?B/HIF-1a signaling pathway. In conclusion, paeoniflorin exerts its anti-inflammatory and anti-fibrotic effects in the liver by coordinating macrophage polarization through the NF-?B/HIF-1a pathway.