Evodiamine alleviates lipopolysaccharide‐induced pulmonary inflammation and fibrosis by activating apelin pathway

Inflammation can cause a series of inflammatory lung disease, which seriously endangers human health. Pulmonary fibrosis is a kind of inflammatory disease with end‐stage lung pathological changes. It has complicated and unknown pathogenesis and is still lack of effective therapeutic drugs. LPS‐induced inflammation is a common feature of many infectious inflammations such as pneumonia, bacteremia, glomerulonephritis, etc. Evodiamine, one of the main components of Evodia rutaecarpa, is an alkaloid with excellent antiinflammatory effects. In this study, we evaluated the protective capacities of evodiamine on LPS‐induced inflammatory damages in vitro and in vivo. MTT method, flow cytometry, immunofluorescence, and other methods were used for in vitro study to determine the protective capacities of evodiamine. The results suggest that evodiamine can protect murine macrophages from the LPS‐nigericin‐induced damages by (a) inhibiting cellular apoptosis, (b) inhibiting inflammatory cytokines releasing, and (c) activating the apelin pathway. We also used the exogenous apelin‐13 peptide co‐cultured with LPS–nigericin in RAW264.7 cells and found that apelin‐13 contributes to protecting the effects of evodiamine. In vivo, the ELISA method and immunohistochemistry were used to examine inflammatory cytokines, apelin, and histological changes. BALB/c mice were exposed to LPS and subsequent administration of evodiamine （p.o.）for some time, the results of the alveolar lavage fluid and the tissue slices showed that evodiamine treatment alleviated the pulmonary inflammation and fibrosis, stimulated apelin expression and inhibited the inflammatory cytokines. These results provide a basis for the protective effect and mechanism of evodiamine in LPS‐induced inflammation and suggest that it might be potential therapeutics in human pulmonary infections.