Abstract
<title>Abstract</title> <p> The gut is under complex attack by a large number of biologically active molecules, including bacterial enzymes, metabolites, nucleic acids and immunoactive compounds. Most of these components are present in outer membrane vesicles (OMVs), which are actively produced by all bacterial types. <italic>Bacteroides fragilis</italic> , a member of the gut microbiota, has unique OMV components that are known to have both pathogenic and positive immunomodulatory properties. The OMVs of <italic>Bacteroides fragilis</italic> are well characterized by proteomic and metabolomic methods and therefore represent a suitable comprehensive framework for assessing the overall molecular impact of bacterial OMVs on intestinal cultures. We studied proteomic changes in colon (HT-29) and rectal (SW837) adenocarcinoma cell lines treated with OMVs isolated from the enterotoxigenic <italic>Bacteroides fragilis</italic> BOB25 strain (ETBF) and the nontoxigenic <italic>Bacteroides fragilis</italic> JIM10 strain (NTBF). The cell lines were incubated with ETBF and NTBF OMVs for three and five hours, after which the total proteomes of the cell lines were isolated and annotated via 2D electrophoresis, followed by mass spectrometric identification of proteomic differences. As a result, the SW837 cell line showed a more significant range of proteome differences than the HT-29 cell line, including not only up- and downregulated proteins involved in cytoskeletal reorganization and cell adhesion but also proteins involved in cell proliferation and the proinflammatory response. We found that SW837 cells treated with NTBF OMVs characterized by high amount of IL18, which plays a profound role in the initiation phase of the immune response by recruiting dendritic cells (DCs). The ETBF OMVs demonstrated the simultaneous coexistence of cell proliferation- and apoptosis-promoting factors. We hypothesize that both types of OMVs may contribute to the observed anti-inflammatory effects, as the same proteins were found to be affected in cell lines treated with ETBF and NTBF OMVs. However, the presence of toxins in ETBF OMVs may delay anti-inflammatory activity until the cell has fully repaired the damaged cytoskeleton. </p>