title: Reorganisation of the salivary mucin network by dietary components: insights from green tea polyphenols.
abstract: The salivary mucins that include MUC5B (gel-forming) and MUC7 (non-gel-forming) are major contributors to the protective mucus barrier in the oral cavity, and it is possible that dietary components may influence barrier properties. We show how one dietary compound, the green tea polyphenol epigallocatechin gallate (EGCG), can substantially alter the properties of both the polymeric MUC5B network and monomeric MUC7. Using rate-zonal centrifugation, MUC5B in human whole saliva and MUC5B purified from saliva sedimented faster in the presence of EGCG. The faster sedimentation by EGCG was shown to be greater with increasing MUC5B concentration. Particle tracking microrheology was employed to determine the viscosity of purified MUC5B solutions and showed that for MUC5B solutions of 200-1600 µg/mL, EGCG caused a significant increase in mucin viscosity, which was greater at higher MUC5B concentrations. Visualisation of the changes to the MUC5B network by EGCG was performed using atomic force microscopy, which demonstrated increased aggregation of MUC5B in a heterogeneous manner by EGCG. Using trypsin-resistant, high-molecular weight oligosaccharide-rich regions of MUC5B and recombinant N-terminal and C-terminal MUC5B proteins, we showed that EGCG causes aggregation at the protein domains of MUC5B, but not at the oligosaccharide-rich regions of the mucin. We also demonstrated that EGCG caused the majority of MUC7 in human whole saliva to aggregate. Furthermore, purified MUC7 also underwent a large increase in sedimentation rate in the presence of EGCG. In contrast, the green tea polyphenol epicatechin caused no change in the sedimentation rate of either MUC5B or MUC7 in human whole saliva. These findings have demonstrated how the properties of the mucin barrier can be influenced by dietary components. In the case of EGCG, these interactions may alter the function of MUC5B as a lubricant, contributing to the astringency (dry puckering sensation) of green tea.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom; Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.
authors.forename: H
authors.initials: H
authors.lastname: Davies-Strickleton
authors.affiliation: Unilever Discover, Shambrook, Bedfordshire, United Kingdom.
authors.forename: Paul D A
authors.initials: PD
authors.lastname: Pudney
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom; Biological Physics, Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom.
authors.forename: Pantelis
authors.initials: P
authors.lastname: Georgiades
authors.affiliation: Biological Physics, Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Waigh
authors.affiliation: BioAFM Facility Centre for Tissue Injury and Repair, Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Hodson
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Ridley
authors.affiliation: Manchester Institute of Biotechnology, Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.
authors.forename: Ewan W
authors.initials: EW
authors.lastname: Blanch
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Thornton
mesh_terms: D028241:Camellia sinensis; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism*; D002501:Centrifugation, Zonal; D004032:Diet; D006801:Humans; D018625:Microscopy, Atomic Force; D055257:Mucin-5B / Q000378:metabolism*; D009077:Mucins / Q000378:metabolism*; D059808:Polyphenols / Q000378:metabolism; D066329:Protein Aggregates; D017434:Protein Structure, Tertiary; D012463:Saliva / Q000378:metabolism*; D012471:Salivary Proteins and Peptides / Q000378:metabolism*; D013662:Tea
chemical_list: C524578:MUC5B protein, human; C083238:MUC7 protein, human; D055257:Mucin-5B; D009077:Mucins; D059808:Polyphenols; D066329:Protein Aggregates; D012471:Salivary Proteins and Peptides; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate