Extraction and Identification of Polysaccharide from Lentinus edodes and Its Effect on Immunosuppression and Intestinal Barrier Injury Induced by Cyclophosphamide

<i>Lentinus edodes</i> serves as a significant source of both medicine and food, with its key component, lentinan (LNT), recognized as an effective immunomodulator. However, the mechanisms by which it regulates immune and intestinal functions under conditions of immunosuppression remain unclear. This study aims to investigate the components of lentinan and examine its potential effects on countering cyclophosphamide (CP)-induced immunosuppression, intestinal barrier damage, and dysregulation of gut microbiota. In this study, the effects of LNT were evaluated by serological indicators, histopathological changes in ileum, tight-junction-related protein expression, cytokine expression levels, and gut microbiota 16S rRNA gene sequencing. We found that LNT was effective in mitigating the abnormalities in body weight, immune organ index, and serum levels of IL-6, IL-2, IFN-γ, and IgG in mice induced by CP (<i>p</i> < 0.05). Furthermore, LNT demonstrated the ability to alleviate intestinal barrier damage induced by CP by increasing the mRNA levels of TNF-α, IL-1β, IFN-γ, Occludin, and ZO-1 (<i>p</i> < 0.05). Additionally, 16S rRNA gene sequencing revealed that LNT also normalized the disrupted abundance of <i>Firmicutes</i>, <i>Proteobacteria</i>, and <i>Bacteroidets</i> caused by CP. This restoration brought the gut microbiota back to normal levels and increased the abundance of certain tumor-inhibiting bacteria, such as <i>Alistipes</i>. Overall, lentinan demonstrated the ability to reverse the immunosuppressive effects induced by cyclophosphamide and modulate gut microbiota to restore a healthy microbial balance.