Immunomodulatory effects of Lactobacillus rhamnosus CRL1505 cellular fractions on human dendritic cells and intestinal epitelial cells

SALVA, SUSANA; TISCORNIA, INÉS; ALVAREZ, SUSANA; ISLA, MARÍA INÉS; BOLLATI-FOGOLÍN, MARIELA

San Miguel deTucumán

Simposio; IV International Symposium on Lactic Acid Bacteria - Food, Health and Applications; 2013

Centro de Referencia para lactobacilos

The use of non-viable lactic acid bacteria and their cellular fractions are excellent alternatives to stimulate immunity in immunocompromised hosts, in which the use of viable microorganisms could involve a risk for health. Previously we demonstrated by in vivo studies that viable Lactobacillus rhamnosus CRL1505 (Lr1505) is able to improve systemic and mucosal immunity in immunocompetent and immunocompromised hosts. The aim of this work was to evaluate the immunoenhancing properties of non-viable Lr1505 and their cellular fractions in order find suitable immunomodulatory products for their application in the recovery of immunocompromised hosts. Viable and ultraviolet (UV)-killed Lr1505 were used in experiments. In addition, intact cell wall (CW), cell wall peptidoglycan (Pg) and intracellular contents (IC) were obtained from Lr1505. NF-kB activation assays were performed in human intestinal epithelial cells (HT-29) stably transfected with plasmid pNF-kB-hrGFP. Transfectants in exponential growth phase were cultured 24 h in the absence or presence of TNF-α and with or without the addition of Lr1505 or its cellular fractions. We demonstrated that 90% of HT29-NF-kB hrGFP cells remained viable after the treatments with Lr1505 or the cellular fractions. Viable and non-viable Lr1505 as well as the cellular fraction were not able to induce activation of NF-kB determined as increased expression of GFP. However Lr1505 and Pg (50 and 100 ug/mL) significantly modulated the NF-kB activation induced by TNF-a (p<0.05). Moreover, only CW and Pg (50 and 100 ug/mL) induced a decrease of IL-8 after stimulation with TNF-α in HT29-NF-kB hrGFP cells. We also used human peripheral blood-derived dendritic cells (DCs) in order to evaluate the immunomodulatory activity of Lr1505. We showed that Lr1505 is efficiently captured and internalized by DCs. In addition, we demonstrated that CW and Pg were able to activate DCs as shown by the increased expression of HLA, CD86, CD80, CD83 and CD40 (p<0.05), and by the production of IL-6, IL-8, IL-10 and TNF-α (p<0.05). Finally, we studied the effect of Lr1505, CW and Pg on human epithelial cells?antigen presenting cells interactions, using the Transwell co-culture system with HT-29 and DCs. In this system, only cell fractions modulated the activation of NF-kB induced by LPS in HT29 cells (p<0.05). CW and Pg increased the expression of surface markers on the DCs in absence of LPS while viable and non-viable Lr1505 modulated the response of these cells against LPS challenge. Non-viable Lr1505, CW and Pg significantly up-regulated the production of IL-6, IL-8, IL-10 and TNF-α in this system. We demonstrated that the immunomodulatory properties of Lr1505 are preserved after the treatment with UV. Moreover, our results showed that both CW and Pg would be responsible, at least in part, for the immunoregulatory effect of the probiotic strain. These results give us the scientific basis for proposing the use of Lr1505 cellular fractions as valid alternatives to improve immunological defenses.