Zhen-wu-tang protects against myocardial fibrosis by inhibiting M1 macrophage polarization via the TLR4/NF-κB pathway

•ZWT showed significantly therapeutic effects on ISO-induced myocardial fibrosis in mice.•ZWT inhibited myocardial fibrosis by inhibiting M1 type macrophage polarization.•ZWT inhibited M1 type macrophage polarization through preventing the activation of TLR4/NF-κB signalling pawthway. Myocardial fibrosis is a risk factor that contributes to the increase in the incidence of cardiovascular disease and death, posing a significant threat to human health. Zhen-wu-tang (ZWT) is a classical Chinese medicinal recipe that has been extensively used to manage cardiovascular disorders throughout history. However, the fundamental processes involved in its effects were not clear. This study examined the therapeutic effects of ZWT on myocardial fibrosis induced by isoproterenol (ISO) in mice, the effect of regulation and underlying mechanism on the polarization of M1 macrophage. In vivo, a myocardial fibrosis mouse model was induced via intraperitoneal infusion of isoproterenol (ISO). ZWT or captopril (CAP) was administered intragastrically for 30 days. Cardiac function was evaluated by electrocardiogram (ECG) and echocardiography. By analysing myocardial fibrosis pathomorphologically and identifying fibrosis-related indicators, the protective effect of the ZWT on the heart was evaluated. A model of macrophage polarization was established in vitro by activating RAW264.7 cells with lipopolysaccharide (LPS). The regulatory effects of ZWT on macrophage polarization and the signalling pathways involved were examined by immunofluorescence staining, Western blotting (WB), quantitative real-time PCR (qRT-PCR) and siRNA transfection. ZWT improved cardiac function; reduced fibrotic deposition in cardiac tissues; decreased α-SMA, collagen I, and collagen III levels; and inhibited myocardial fibrosis in mice with ISO-induced myocardial fibrosis. Furthermore, the results showed that ZWT could suppress M1 macrophage polarization by downregulating the expression of CD86 and iNOS in vitro and in vivo. Finally, the results confirmed that ZWT could significantly reduce TLR4/NF-κB signalling pathway activation. ZWT showed therapeutic effects on ISO-induced myocardial fibrosis mice, and reduced M1 macrophages polarization through inhibiting TLR4/NF-κB pathway, suggesting that ZWT is a promising drug for myocardial fibrosis treatment. [Display omitted]