Euglena Gracilis and β-Glucan Paramylon Induce Ca(2+) Signaling in Intestinal Tract Epithelial, Immune, and Neural Cells

The intestinal tract contains over half of all immune cells and peripheral nerves and manages the beneficial interactions between food compounds and the host. Paramylon is a β-1,3-glucan storage polysaccharide from Euglena gracilis (Euglena) that exerts immunostimulatory activities by affecting cytokine production. This study investigated the signaling mechanisms that regulate the beneficial interactions between food compounds and the intestinal tract using cell type-specific calcium (Ca(2+)) imaging in vivo and in vitro. We successfully visualized Euglena- and paramylon-mediated Ca(2+) signaling in vivo in intestinal epithelial cells from mice ubiquitously expressing the Yellow Cameleon 3.60 (YC3.60) Ca(2+) biosensor. Moreover, in vivo Ca(2+) imaging demonstrated that the intraperitoneal injection of both Euglena and paramylon stimulated dendritic cells (DCs) in Peyer’s patches, indicating that paramylon is an active component of Euglena that affects the immune system. In addition, in vitro Ca(2+) imaging in dorsal root ganglia indicated that Euglena, but not paramylon, triggers Ca(2+) signaling in the sensory nervous system innervating the intestine. Thus, this study is the first to successfully visualize the direct effect of β-1,3-glucan on DCs in vivo and will help elucidate the mechanisms via which Euglena and paramylon exert various effects in the intestinal tract.