LAUSR

Background Reduning (RDN) is a common Chinese medicine preparation with antibacterial, anti-inflammatory, antiviral and immunomodulatory effects in respiratory infectious diseases. Clinically, it is used in combination with antibiotics, but its synergistic effect and mechanism in treating severe pneumonia remain unclear. Methods A rat model of severe pneumonia and an in vitro coculture model consisting of A549 and THP-1 cells were used to observe the synergistic effect of RDN on severe pneumonia. The inflammatory cytokines were tested by enzyme-linked immunosorbent assay (ELISA). The localization of Aryl hydrocarbon receptor (AhR) in A549 cells was observed by immunofluorescence, and the interaction of AhR and signal transducer and activator of transcription 3 (STAT3) proteins was observed by co-immunoprecipitation. AhR-Src tyrosine kinase (Src)-STAT3 pathway in rats and A549 cells were examined by Western Blot. Histopathological changes were observed by Hematoxylin-eosin (HE) staining, X-ray and survival rates were used to evaluate the effects of paclitaxel on severe pneumonia rats. Results RDN regulation of Src-STAT3-interleukin 10 (IL-10) signaling pathway activation and macrophage polarization were mediated through the nuclear receptor AhR. The expression of AhR was significantly increased after RDN treatment, and this effect was accompanied by STAT3 expression increasing. Coimmunoprecipitation confirmed an interaction between AhR and STAT3 and upregulated IL-10 expression. Silencing AhR decreased Src, STAT3, and IL-10 expression. RDN activated AhR and increased Src, STAT3, and IL-10 expression. In addition, RDN regulated the polarization of macrophages RDN combined with cefmetazole sodium significantly reduced the pulmonary bacterial load, alleviated lung injury, and reduced o inflammatory factors expression, improving their survival. Conclusions RDN can synergistically enhance the effect of cefmetazole sodium treatment in severe pneumonia, and the mechanism may involve increasing the expression level of IL-10 mediated through the AhR-Src-STAT3 pathway, driving the polarization of macrophages, and attenuating the cytokine storm to control inflammation in severe pneumonia.