Promising immunomodulatory effects of selected strains of dairy propionibacteria
Résumé
Inflammatory bowel disease (IBD) constitutes a growing health concern in developed countries. Augmentation of its incidence seems related to the westernized lifestyle, including changes in the diet. The exact mechanisms involved in the etiology of IBD are not completely elucidated, but indigenous intestinal bacteria play a key pro-inflammatory role in it. Selected immunomodulatory probiotic bacteria can counteract inflammation of the intestine through regulatory activities. This involves cross-talk with immune and epithelial cells at the intestine level and induction of regulatory cytokines. Probiotic strains able to induce anti-inflammatory cytokines in human peripheral blood mononucleated cells (PBMCs) in vitro were shown to exert efficient anti-inflammatory effects on colitis in vivo. However, little is known about the immunomodulatory potential of starter bacteria consumed in high amounts in traditional fermented dairy products, including dairy propionibacteria. Available literature, however, suggests an antiinflammatory potential for a strain of P. freudenreichii. We thus investigated immunomodulatory properties of various strains of this bacterium on PBMCs. This included strains used as cheese ripening cultures and strains used as probiotics for human consumption. This investigation revealed a great diversity in the immunomodulatory profile, depending on the strain. One strain, showing a particularly anti-inflammatory profile, was further tested on distinct experimental models of colitis in mice. The promising protective effects observed in vivo suggest that selected strains of dairy propionibacteria and/or fermented dairy products containing these bacteria may be useful in a preventive diet designed to prevent or limit the severity of IBD in humans.