Lactobacilli strains enhanced Human β defensin 2 (HBD2) expression in flagellin-induced model of cultured intestinal cells.

HUGO, A. A.; SZYMANOWSKI, F. AND PÉREZ, P. F.

Otro; LXVI Reunión Anual de la Sociedad Argentina de Inmunología.; 2019

Human defensins are small cationic peptides which contribute to the mucosal host defences. Gut epithelia produce β-defensins (HBD-1 and HBD-2). HBD-1 has a constitutive expression whereas HBD-2 is inducible by endogenous stimuli such as inflammatory cytokines or by exogenous microbial factors (PAMPs) in a toll-dependent manner. HBD-2 expression is promoted by NF-kB. Certain probiotic strains could exhibit immunomodulatory effects at intestinal level including the induction of HDB-2 expression. The aim of this study is to investigate the capacity of two lactobacilli strains (L. delbrueckii subsp lactis CIDCA 133 and L. delbrueckii subsp bulgaricus, CIDCA 331) to induce HBD-2 expression in a human enterocyte-like cells (Caco-2 and HT-29). Monolayers were incubated with lactobacilli (20 bacteria per cell) for 24 h at 37°C. HBD-2 expression was measured by qPCR. Positive controls were stimulated with flagellin from Salmonella sp. (FliC). NF-KB expression was assessed by using a reporter HT-29 cell line. Lactobacilli strains alone were unable to induce HBD-2 expression. However, the co-incubation of cells with lactobacilli and flagellin significantly increased HBD-2 expression. UVor heat-killed strains had also the capacity of inducing HBD-2 expression. Lactobacilli strains per se were unable to increase the expression of NF-kB. Previous incubation of the intestinal cells with lactobacilli followed by FliC stimulation reduced by 50% the percentage of NF-kB positive cells. Results showed that the lactobacilli strains enhanced the HBD-2 expression induced by FliC. The FliC pathway involves TLRs and expression of NF-kB. Interestingly, lactobacilli down-regulated the NF-kB expression. Several proinflammatory and antimicrobial factors are up-regulated by NF-kB. Lactobacilli strains under study had the capacity to stimulate the expression of HBD-2 without exacerbate NF-kB response thus indicating a non-inflammatory pathway of modulation.