Prevention of cyclophosphamide-induced immune suppression by polysaccharides from Apocynum venetum flowers via enhancing immune response, reducing oxidative stress, and regulating gut microbiota in mice

Introduction Emerging proof suggests that Apocynum venetum flowers polysaccharide (AVFP) has immunomodulatory effects in vitro . However, the action mechanism of AVFA is still unclear in vivo . The purpose of this study is to probe into the potential mechanism of AVFA in immunosuppressed mice by investigating organ index, cytokine levels, anti-oxidative stress capacity, transcriptomics, and gut microbiota. Methods Immunocompromised mice induced by cyclophosphamide (CTX) were divided into six groups. The enzyme-labeled method, hematoxylin and eosin, transcriptomics, and high-throughput sequencing were used to detect the regulatory effects of AVFP on immunocompromised mice and the function of AVFP on the concentration of short-chain fatty acids (SCFAs) by high-performance liquid chromatography (HPLC) analysis. The Spearman correlation analysis was used to analyze the correlation between the intestinal microbiota and biochemical indexes. Results The experimental results illustrated that AVFP has protective effects against CTX-induced immunosuppression in mice by prominently increasing the organ index and levels of anti-inflammatory factors in serum in addition to enhancing the antioxidant capacity of the liver. Meanwhile, it could also signally decrease the level of pro-inflammatory cytokines in serum, the activity of transaminase in serum, and the content of free radicals in the liver, and alleviate the spleen tissue damage induced by CTX. Transcriptomics results discovered that AVFP could play a role in immune regulation by participating in the NF- κ B signaling pathway and regulating the immune-related genes Bcl3 , Hp , Lbp , Cebpd , Gstp2 , and Lcn2 . Gut microbiota results illustrated that AVFP could increase the abundance of beneficial bacteria, reduce the abundance of harmful bacteria, and regulate the metabolic function of intestinal microorganisms while dramatically improving the content of SCFAs, modulating immune responses, and improving the host metabolism. The Spearman analysis further evaluated the association between intestinal microbiota and immune-related indicators. Conclusion These findings demonstrated that AVFP could enhance the immune effects of the immunosuppressed mice and improve the body’s ability to resist oxidative stress.