title: Immunomodulation of monocytes by probiotic and selected lactic Acid bacteria.
abstract: Some lactic acid bacteria (LAB), especially bacteria belonging to the genus Lactobacillus, are recognized as common inhabitants of the human gastrointestinal tract and have received considerable attention in the last decades due to their postulated health-promoting effects. LAB and probiotic bacteria can modulate the host immune response. However, much is unknown about the mediators and mechanisms responsible for their immunological effect. Here, we present a study using cytokine secretion from the monocytic cell line THP-1 and NF-κB activation in the monocytic cell line U937-3xkB-LUC to elucidate immune stimulating abilities of LAB in vitro. In this study, we investigate both commercially available and potential probiotic LAB strains, and the role of putative surface proteins of L. reuteri using mutants. L. reuteri strains induced the highest cytokine secretion and the highest NF-κB activation, whereas L. plantarum strains and L. rhamnosus GG were low inducers/activators. One of the putative L. reuteri surface proteins, Hmpref0536_10802, appeared to be of importance for the stimulation of THP-1 cells and the activation of NF-κB in U937-3xkB-LUC cells. Live and UV-inactivated preparations resulted in different responses for two of the strains investigated. Our results add to the complexity in the interaction between LAB and human cells and suggest the possible involvement of secreted pro- and anti-inflammatory mediators of LAB. It is likely that it is the sum of bacterial surface proteins and bacterial metabolites and/or secreted proteins that induce cytokine secretion in THP-1 cells and activate NF-κB in U937-3xkB-LUC cells in this study.
authors.affiliation: Nofima, Norwegian Institute of Food, Fisheries, and Aquaculture Research, P.O. Box 210, 1431, Ås, Norway, hanne.jensen@nofima.no.
authors.forename: Hanne
authors.initials: H
authors.lastname: Jensen
authors.forename: Signe Marie
authors.initials: SM
authors.lastname: Drømtorp
authors.forename: Lars
authors.initials: L
authors.lastname: Axelsson
authors.forename: Stine
authors.initials: S
authors.lastname: Grimmer
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D056747:Immunomodulation; D007778:Lactobacillus / Q000502:physiology* / Q000528:radiation effects; D009000:Monocytes / Q000378:metabolism / Q000382:microbiology*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D019936:Probiotics; D020298:U937 Cells; D014466:Ultraviolet Rays
chemical_list: D016328:NF-kappa B