What interactions drive the salivary mucosal pellicle formation?

Hannah L Gibbins,Gleb E Yakubov,Gordon B Proctor,Stephen Wilson,Guy H Carpenter

doi:10.1016/j.colsurfb.2014.05.020

Hannah L Gibbins, Gleb E Yakubov + Show 3 more

Open Access

https://doi.org/10.1016/j.colsurfb.2014.05.020

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Abstract

The bound salivary pellicle is essential for protection of both the enamel and mucosa in the oral cavity. The enamel pellicle formation is well characterised, however the mucosal pellicle proteins have only recently been clarified and what drives their formation is still unclear. The aim of this study was to examine the salivary pellicle on particles with different surface properties (hydrophobic or hydrophilic with a positive or negative charge), to determine a suitable model to mimic the mucosal pellicle. A secondary aim was to use the model to test how transglutaminase may alter pellicle formation. Particles were incubated with resting whole mouth saliva, parotid saliva and submandibular/sublingual saliva. Following incubation and two PBS and water washes bound salivary proteins were eluted with two concentrations of SDS, which were later analysed using SDS-PAGE and Western blotting. Experiments were repeated with purified transglutaminase to determine how this epithelial-derived enzyme may alter the bound pellicle. Protein pellicles varied according to the starting salivary composition and the particle chemistry. Amylase, the single most abundant protein in saliva, did not bind to any particle indicating specific protein binding. Most proteins bound through hydrophobic interactions and a few according to their charges. The hydrophobic surface most closely matched the known salivary mucosal pellicle by containing mucins, cystatin and statherin but an absence of amylase and proline-rich proteins. This surface was further used to examine the effect of added transglutaminase. At the concentrations used only statherin showed any evidence of crosslinking with itself or another saliva protein.In conclusion, the formation of the salivary mucosal pellicle is probably mediated, at least in part, by hydrophobic interactions to the epithelial cell surface.

Highlights

The bound mucosal pellicle The oral mucosa has to be extremely tough to withstand the extreme conditions it is exposed to, such as the abrasive action and temperature extremes associated with an extremely wide range of foods in the human diet
Which proteins bind to the different surface types? A number of salivary proteins bound to all particle types, see figure 1, most bound to at least one particle and a few highly abundant proteins didn’t bind at all
The result can be explained if we suggest that binding to positively charged particles is so strong that binding kinetics favours very quick adsorption of highly negative species such as aPRPs

Summary

Introduction

The bound mucosal pellicle The oral mucosa has to be extremely tough to withstand the extreme conditions it is exposed to, such as the abrasive action and temperature extremes associated with an extremely wide range of foods in the human diet. MUC5B and MUC7 are key for providing layer protection and lubrication due to their high molecular weight and high level of hydration which is due to presence of highly glycosylated regions. Both type of salivary mucins are found to be strongly retained on the buccal cell surfaces (Amerongen, Bolscher et al 1995; Tabak 1995), while within tooth enamel pellicle the mucin composition is dominated by MUC5B (Cardenas, Elofsson et al.2007). The key element of the assembly process is the formation of a tightly bound layer that ensures adhesion of the pellicle and acts as a template for further protein/mucin assembly

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