DNA from probiotic bacteria modulates murine and human epithelial and immune function

Abstract Background & Aims: The intestinal epithelium must discriminate between pathogenic and nonpathogenic bacteria and respond accordingly. The aim of this study was to examine whether bacterial DNA can serve as the molecular basis for bacterial recognition. Methods: HT-29 monolayers were treated with various bacterial DNA and interleukin (IL)-8 secretion measured by enzyme-linked immunosorbent assay, nuclear factor κB activation by electrophoretic mobility shift assay and reporter assays, and IκB levels by Western blotting. Cytokine secretion in response to bacterial DNA was measured in murine colonic segments and splenocytes. IL-10–deficient mice were fed DNA from VSL probiotic compound daily for 2 weeks. Colons were removed and analyzed for cytokine production and inflammation. Results: HT-29 cells responded with IL-8 secretion to bacterial DNA in a differential manner. In the presence of proinflammatory stimuli, VSL3 DNA inhibited IL-8 secretion, reduced p38 mitogen-activated protein kinase activation, delayed nuclear factor κB activation, stabilized levels of IκB, and inhibited proteasome function. VSL3 DNA inhibited colonic interferon (IFN)-γ secretion in mouse colons and also attenuated a Bacteroides vulgatus –induced IFN-γ release from murine splenocytes. In mice, VSL3 DNA attenuated a systemic release of tumor necrosis factor α in response to Escherichia coli DNA injection. Treatment of IL-10–deficient mice with oral VSL3 DNA resulted in a reduction in mucosal secretion of tumor necrosis factor α and IFN-γ and an improvement in histologic disease. Conclusions: DNA from probiotic bacteria can limit epithelial proinflammatory responses in vivo and in vitro. Systemic and oral administration of VSL3 DNA ameliorates inflammatory responses.