β-glucans from Coriolus versicolor protect mice against S. typhimurium challenge by activation of macrophages

•There are no detectable cytotoxic effects of β-glucans.•β-glucans induce strong proliferaion and expresion of CD40, CD80, and CD86 marker of macrophages.•β-glucans-treated macrophage but not itself can phagocytize and kill S. typhimurium.•β-glucans induce the production of NO and iNOS from pretreated macrophages.•β-glucans-treated macrophages are effective at protecting mice against the challenge of S. typhimurium. The effects of β-glucans from Coriolus versicolor (CVP), which are extracted from a well-known immune stimulator C. versicolor, have been demonstrated extensively in vitro and in vivo. However, until now, the phagocytic activity has not been elucidated. Hence, the objective of the present study was to identify the antibacterial activity of CVP or CVP-treated macrophages by an analysis of cell cytotoxicity, phagocytic activity, intracellular bacterial survival, macrophage activation, production of nitric oxide (NO) and expression of inducible nitric oxide synthase (iNOS) in CVP-treated macrophages using flow cytometry, RT-PCR, a gentamicin protection assay, a Nitric oxide assay and an iNOS enzymatic activity assay. The results indicate that CVP-treated macrophages can phagocytize and kill bacteria, probably due to the production of NO and iNOS. More importantly, CVP-treated macrophages are effective at protecting mice against the challenge of Salmonella typhimurium. The results of this study suggest that the antibacterial effects of CVP are probably caused by the activation of innate immune cells, especially macrophages, because the activated macrophage produces NO, which kills bacteria. These phenomena indicate the possibility of CVP as a potential alternative for antibiotics against resistant bacteria.