Immunomodulatory mechanisms exerted by probiotic bacteria in the intestinal mucosa immune system

LEMME DUMIT, J.M.; SAAVEDRA, L.; HEBERT, E.M.; PERDIGON, G.; MALDONADO GALEANO, C.

Congreso; LXV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI); 2017

Probioticsbacteria can interact with mucosal immune cells or epithelial cells lining themucosa to modulate specific functions of the mucosal immune system. Here, weaimed to study the differences in the mechanisms exerted by probiotic bacteriaand its cell wall in the gut mucosa, compared with an enteropathogenicbacteria. Six wk-old BALB/c mice received in the drinking water a suspension ofviable Lactobacillus casei CRL431 (Lc431) (108 CFU/mL) or by gavage its cellwall (CW431) (100 mL/day) for 7 days, d8 animals were sacrificed. One dose ofSalmonella Typhimurium (108 CFU/mL) were performed on 6-wk-old BALB/c mice,after 72 h animals were sacrificed. Relative fold change gene expression (a20,irak-m, mkp-1, and tollip) were determined on intestinal epithelial cells (IEC)and on peritoneal macrophages (pMf) by RT-qPCR. The percentages of Treg andTh17 cells were analyzed on the lamina propria of the gut by flow cytometry.Lc431 and its CW431 were able to increase significantly the regulatory genesexpression of NF-kB and MAPK pathways on IEC and pMf compared to Salmonella(p<0.05). At the same time, Lc431 and its CW431 increased the percentages ofCD4+ CD25+ Foxp3+ IL-10+ cells in the lamina propria of the gut compared tountreated and Salmonella mice (p<0.05). However, there were not differenceson CD4+ IL-17+ cells percentages, in all conditions evaluated (p<0.05).Previously, we demonstrated that probiotics active the NF-kB pathway, howeverprobiotics are not an inflammatory stimulus to the gut mucosa. In this sense,the present results suggest that probiotic up-regulates the regulatory proteinsof NF-kB and MAPK pathways modulating the immune response on IEC and pMf, incontrast to Salmonella infection. In this scenario, IEC could create thecytokine environment that favor the balance to Treg profile in the gut laminapropria. These results would demonstrate the way by which probiotics are ableto modulate the gut mucosal immune system.Keywords:probiotic, probiotic cell wall, regulatory proteins, immunomodulation, gut homeostasis