A Novel Rhamnose-Rich Hetero-exopolysaccharide Isolated from Lactobacillus paracasei DG Activates THP-1 Human Monocytic Cells

Abstract

Lactobacillus paracasei DG is a bacterial strain with recognized probiotic properties and is used in commercial probiotic products. However, the mechanisms underlying its probiotic properties are mainly unknown. In this study, we tested the hypothesis that the ability of strain DG to interact with the host is at least partly associated with its ability to synthesize a surface-associated exopolysaccharide (EPS). Comparative genomics revealed the presence of putative EPS gene clusters in the DG genome; accordingly, EPS was isolated from the surface of the bacterium. A sample of the pure EPS from strain DG (DG-EPS), upon nuclear magnetic resonance (NMR) and chemical analyses, was shown to be a novel branched hetero-EPS with a repeat unit composed of L-rhamnose, D-galactose, and N-acetyl-D-galactosamine in a ratio of 4:1:1. Subsequently, we demonstrated that DG-EPS displays immunostimulating properties by enhancing the gene expression of the proinflammatory cytokines tumor necrosis factor alpha (TNF-␣) and interleukin 6 (IL-6), and particularly that of the chemokines IL-8 and CCL20, in the human monocytic cell line THP-1. In contrast, the expression of the cyclooxygenase enzyme COX-2 was not affected. In conclusion, DG-EPS is a bacterial macromolecule with the ability to boost the immune system either as a secreted molecule released from the bacterium or as a capsular envelope on the bacterial cell wall. This study provides additional information about the mechanisms supporting the cross talk between L. paracasei DG and the host. IMPORTANCEThe consumption of food products and supplements called probiotics (i.e., containing live microbial cells) to potentially prevent or treat specific diseases is constantly gaining popularity. The lack of knowledge on the precise mechanisms supporting their potential health-promoting properties, however, greatly limits a more appropriate use of each single probiotic strain. In this context, we studied a well-known probiotic, Lactobacillus paracasei DG, in order to identify the constitutive molecules that can explain the documented health-promoting properties of this bacterium. We found a novel polysaccharide molecule, named DG-EPS, that is secreted by and covers the bacterium. We demonstrated that this molecule, which has a chemical structure never identified before, has immunostimulatory properties and therefore may contribute to the ability of the probiotic L. paracasei DG to interact with the immune system. KEYWORDS

Characterization of the SN35N Strain-Specific Exopolysaccharide Encoded in the Whole Circular Genome of a Plant-Derived <i>Lactobacillus plantarum</i>

“…44,45) The present study shows that the IC 50 value for the SN35N-derived acidic EPS to hyaluronidase has almost the same as those of sodium cromoglicate and dipotassium glycyrrhizinate used as an anti-inflammatory agent (hyaluronidase inhibitors). 45,46) Interestingly, although our previous report has showed that the neutral EPS produced by P. pentosaceus LY45 inhibits hyaluronidase activity more effectively than did the acidic EPS, including fucoidan. 22) The IC 50 value of the SN35N-derived acidic EPS is significantly lower than those of the acidic ones.…”

“…Furthermore, it has been shown that some Lactobacillus strains, such as Lb. paracasei DG, 47) Lb. casei YIT9018, 48) and Lb.…”

Evidence for the Modulation of the Immune Response in Peripheral Blood Mononuclear Cells after Stimulation with a High Molecular Weight β-glucan Isolated fromLactobacillus fermentumLf2

“…The monosaccharides present were determined after acid hydrolysis either directly using HPAEC-PAD analysis or as their alditol acetates, as previously described(12). The absolute configuration of the sugars was determined by preparation of their respective 2-( S )-butylglycosides using Gerwig’s method(52).…”

“…The strain produces significant quantities of a mixture of EPS (∼2g/L) and it has been demonstrated that the crude EPS has immunomodulatory activity (11). In previous studies, using EPS from lactic acid bacteria (12; 13), we have shown that specific EPS can stimulate production of pro- and anti-inflammatory cytokines. We also provided evidence that the EPS can modulate the immune response and in doing so provide a degree of immunotolerance.…”

Health promoting activities of probiotics

“…Many other studies revealed that exopolysaccharides (EPS) could modulate the immune system. A previous study fully elucidated that a novel rhamnose‐rich heteroexopolysaccharide isolated from L. paracasei DG may activate human monocytic cells by increasing the gene expression of proinflammatory cytokines combined with chemokine (C‐C motif) ligand 20 (CCL20) (Balzaretti et al, ). By contrast, Vinderola, Perdigon, Duarte, Farnworth, and Matar () revealed that exopolysaccharide extracted from L. kefiranofaciens strengthened intestinal mucosal immunity through increasing IgA+ cells, leading to enhancement of IgA production (Vinderola et al, ).…”