Inulin induces dendritic cells apoptosis through the caspase-dependent pathway and mitochondrial dysfunction

Dendritic cells are professional antigen-presenting cells that are responsible for initiating of the immune response. However, there are no reports on how the polysaccharides in an oral biofilm affect the viability of dendritic cells. Inulin, a fructooligossacharide, is one component of oral biofilm fructan that is used as an energy source by oral bacteria. In this study, we found that murine bone marrow derived dendritic cells were induced to undergo apoptosis after being treated with inulin in a dose-dependent manner, as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), annexinV/propidium iodide (PI), and Hoechest staining methods. Inulin activated the apoptotic pathway, including caspase-9 and caspase-3, decreased the level of B-cell lymphoma 2 (Bcl-2) expression, increased the expression of the Bcl-2-associated X protein (Bax) protein and induced poly(ADP-ribose) polymerase (PARP) cleavage. These observations suggest that inulin induces the apoptosis of dendritic cells by altering the Bcl-2/Bax ratio through the caspase dependant pathway. These results indicated that high concentrations of inulin can cause apoptic cell death in murine bone marrow-derived dendritic cells.