title: 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-α) 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.
  
  
  
  The 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.
authors.affiliation: Division of Food Microbiology and Bioprocesses, Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Balzaretti
authors.affiliation: Division of Food Microbiology and Bioprocesses, Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Taverniti
authors.affiliation: Division of Food Microbiology and Bioprocesses, Department of Food, Environmental and Nutritional Sciences (DeFENS), Università degli Studi di Milano, Milan, Italy simone.guglielmetti@unimi.it a.p.laws@hud.ac.uk.
authors.forename: Simone
authors.initials: S
authors.lastname: Guglielmetti
authors.affiliation: Sofar S.p.A., Trezzano Rosa, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Fiore
authors.affiliation: Department of Biosciences, Università degli Studi di Milano, Milan, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Minuzzo
authors.affiliation: Department of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield, United Kingdom.
authors.forename: Hansel N
authors.initials: HN
authors.lastname: Ngo
authors.affiliation: Department of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield, United Kingdom.
authors.forename: Judith B
authors.initials: JB
authors.lastname: Ngere
authors.affiliation: Department of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield, United Kingdom.
authors.forename: Sohaib
authors.initials: S
authors.lastname: Sadiq
authors.affiliation: Department of Biological Sciences, University of Huddersfield, Queensgate, Huddersfield, United Kingdom.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Humphreys
authors.affiliation: Department of Chemical Sciences, University of Huddersfield, Queensgate, Huddersfield, United Kingdom simone.guglielmetti@unimi.it a.p.laws@hud.ac.uk.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Laws
mesh_terms: D002460:Cell Line; D015870:Gene Expression; D006801:Humans; D000069980:Lacticaseibacillus paracasei / Q000502:physiology*; D009000:Monocytes / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000502:physiology*; D012210:Rhamnose / Q000737:chemistry
chemical_list: D011135:Polysaccharides, Bacterial; D012210:Rhamnose
keywords: Capsular EPS; Enterolactis; Lactobacillus casei DG; Lactobacillus paracasei; MAMPs; THP-1; immunostimulation; probiotic