Protective Mechanism Of Codonopsis Polysaccharide On Acute Lung Injury Induced By Escherichia Coli In Mice

Acute lung injury(ALI)is a lung disease caused by an inflammatory response or bacterial infection.It mainly presents as acute respiratory distress syndrome(ARDS)in affected animals.Studies have shown that Codonopsis pilosula polysaccharides(CPPS),the main component of Codonopsis pilosula extract,can activate immune cells,but it is not clear whether it can regulate the inflammatory response and organ damage induced by Escherichia coli(E.coli)and its bacterial components in mice.In this study,in vitro and in vivo experiments were conducted to explore the regulatory mechanism of CPPS on E.coli and its bacterial components induced inflammatory response and organ damage in mice.In vitro raises the C57BL/6J mice abdominal cavity macrophage,CPPS pretreatment cells with different concentration of 1 h,reoccupy lipopolysaccharide(LPS),Braun lipoprotein(BLP)and Wild type Escherichia coli(WT E.coli)stimulate the peritoneal macrophages in mice,by ELISA method to detect the secretion of inflammatory mediators.The activation of macrophage inflammatory signaling pathway in mice was detected by Western blot.To analyze the effects of CPPS on the growth of WT E.coli and the ability of macrophages to kill bacteria.In the vivo experiment,mice were intraperitoneally injected with different concentrations of CPPS,and Dexamethasone(DEX)group was used as the positive treatment control group.The mice were pretreated for 1 h,and then the acute lung injury model was established by nasal aspiration of LPS,BLP and WT E.coli.The secretion level of pulmonary inflammatory mediators in mice was detected by ELISA.The expression of high mobility group protein B1(HMGB1)and hyaluronic acid binding protein 2(HABP2)in the lungs of mice was detected by immunofluorescence assay.HE staining was used to observe the lung damage and pathological changes of mice.The results showed that CPPS was non-cytotoxic and could regulate the secretion of inflammatory cytokines(TNF-α,IL-1β,IL-6)and chemokines(RANTES)induced by LPS,BLP and WT E.coli.At the same time,CPPS also has a certain regulation effect on the activation of NF-κB p65,MAPKs p38 and ERK induced by LPS,BLP and WT E.coli.In addition,CPPS inhibited the growth of E.coli and up-regulated the killing ability of macrophages against E.coli(P < 0.05).CPPS down-regulated the secretion of TNF-α,IL-1β,LI-6 and RANTES in mice stimulated by LPS and WT E.coli(P < 0.001)and up-regulated the secretion of IL-1β,IL-6 and RANTES after BLP stimulation.In addition,CPPS can down-regulate the expression of HMGB1 and HABP2 proteins in lung damage markers of mice stimulated by LPS,BLP and WT E.coli,and CPPS can also protect the lung damage of mice infected by WT E.coli.In conclusion,in vivo CPPS of LPS and WT E.coli after stimulation induce the secretion of inflammatory mediators have down-regulate,for the BLP stimulation induce the secretion of inflammatory mediators have up-regulate,after the team speculated that as a kind of E.coli outer membrane composition BLP,the E.coli is not the main induced mice inflammatory mediator secreted by immune active ingredients,and the existence of CPPS can significantly increase induced by BLP secretion of inflammatory mediators,the emergence of this phenomenon is beneficial to the host’s immune system to remove E.coli,and then down-regulate the tissue damage induced by E.coli,such as lung damage process has a protective effect.This study showed that CPPS,as an immunomodulator,plays an important role in regulating and protecting host inflammatory response and lung damage caused by E.coli infection,inhibiting the proliferation of bacteria,and enhancing the killing ability of macrophages against E.coli.The elucidations of this mechanism provide a scientific and effective theoretical basis for the use of CPPS,and its analogues to effectively prevent,and treat host lung damage and inflammatory diseases caused by E.coli infection in veterinary clinical practice.