Impact of a bifidobacterial strain on intestinal inflammation in different models of murine colitis

Abstract

Different strains of probiotic bifidobacteria have shown their potential in the treatment of chronic intestinal inflammation, e.g. in inflammatory bowel diseases. In the present study the anti-inflammatory properties of B. bifidum S17 were analysed in vivo in a Rag1-/- and a DSS-induced murine model of colitis. Also further in vivo and in vitro experiments were performed to investigate the bifidobacterial effects on the level of the mucosal immune system. Collectively, the presented data demonstrate that treatment with B. bifidum S17 significantly reduces clinical symptoms and markers in two models of chronic intestinal inflammation. In line with data from other studies, both models are characterized by a strong Th1 response, as evidenced by increased tissue levels of the pro-inflammatory cytokines IL-6, TNFalpha and IFNgamma. Treatment with B. bifidum S17 led to a decrease in these cytokines and/or their respective T cell populations in one or both models. Furthermore, B. bifidum S17 improved intestinal inflammation by inhibition of T cell proliferation and skewing of the T cell pool towards a higher frequency of Foxp3+ TRegs. The TReg polarizing effect could be reproduced in vitro by co-culture of dendritic cells with naïve T cells in the presence of B. bifidum S17. Additional in vivo experiments indicate a contribution of the CX3CR1+high dendritic cell population, which has been shown to support TReg development, to the anti-inflammatory effect. Further studies are required to identify the bacterial structures as well as to dissect the exact immunological mechanisms involved in the effects of B. bifidum S17.