Changes in mouse whole saliva soluble proteome induced by tannin-enriched diet

Abstract

Background: Previous studies suggested that dietary tannin ingestion may induce changes in mouse salivary proteins in addition to the primarily studied proline-rich proteins (PRPs). The aim of the present study was to determine the protein expression changes induced by condensed tannin intake on the fraction of mouse whole salivary proteins that are unable to form insoluble tannin-protein complexes. Two-dimensional polyacrylamide gel electrophoresis protein separation was used, followed by protein identification by mass spectrometry.

Results: Fifty-seven protein spots were excised from control group gels, and 21 different proteins were identified. With tannin consumption, the expression levels of one α-amylase isoform and one unidentified protein increased, whereas acidic mammalian chitinase and Muc10 decreased. Additionally, two basic spots that stained pink with Coomassie Brilliant Blue R-250 were newly observed, suggesting that some induced PRPs may remain uncomplexed or form soluble complexes with tannins.

Conclusion: This proteomic analysis provides evidence that other salivary proteins, in addition to tannin-precipitating proteins, are affected by tannin ingestion. Changes in the expression levels of the acidic mammalian chitinase precursor and in one of the 14 salivary α-amylase isoforms underscores the need to further investigate their role in tannin ingestion.

Figure 1

Examination by ligth microscopy of parotid glands. Original magnification X200 (bar = 50 μm). Acini from control group (A) are significantly lower than those from quebracho tannin-enriched diet group (B). a - acinus; d - salivary ducts.

Figure 2

Two-dimensional proteome profile of mice whole saliva. Aliquots containing 100 μg of proteins from control animals were subjected to IEF in a 3-10 NL range, separated by molecular masses in 12% polyacrylamide gels and stained with Coomassie Coloidal G-250. Molecular markers masses are represented on the left side of the gel. Numbered protein spots were collected for protein identification.

Figure 3

Changes in the proteome of mice whole saliva after quebracho consumption. A) representative gel of an individual from control group; B) representative gel of an individual of quebracho group. A decrease in relative volume was observed for spot 38, whereas spots 24 and 62 increased after quebracho consumption. Spot 30 was only observed in the gels from control group, whereas spots Q1 and Q2 were only observed in 2-DE gels from quebracho group. These last spots were dark pink stained. Coloured pictures are presented in supplementary Figure S1. Some of the spots for which expression levels are different in this figure did not change consistently in all individuals and, consequently, are not discussed.