iTRAQ-based quantitative analysis of age-specific variations in salivary proteome of caries-susceptible individuals

Abstract

BackgroundHuman saliva is a protein-rich, easily accessible source of potential biomarkers for the diagnosis of oral and systemic diseases. However, little is known about the changes in salivary proteome associated with aging of patients with dental caries. Here, we applied isobaric tags for relative and absolute quantitation (iTRAQ) in combination with multiple reaction monitoring mass spectrometry (MRM-MS) to characterize the salivary proteome profiles of subjects of different ages, presenting with and without caries, with the aim of identifying age-related biomarkers for dental caries.MethodsUnstimulated whole saliva samples were collected from 40 caries-free and caries-susceptible young adults and elderly individuals. Salivary proteins were extracted, reduced, alkylated, digested with trypsin and then analyzed using iTRAQ-coupled LC–MS/MS, followed by GO annotation, biological pathway analysis, hierarchical clustering analysis, and protein–protein interaction analysis. Candidate verification was then conducted using MRM-MS.ResultsAmong 658 salivary proteins identified using tandem mass spectrometry, 435 proteins exhibited altered expression patterns in different age groups with and without caries. Of these proteins, 96 displayed age-specific changes among caries-susceptible adults and elderly individuals, and were mainly associated with salivary secretion pathway, while 110 age-specific proteins were identified among healthy individuals. It was found that the age factor caused significant variations and played an important role in both healthy and cariogenic salivary proteomes. Subsequently, a total of 136 target proteins with complex protein–protein interactions, including 14 age-specific proteins associated with caries, were further successfully validated using MRM analysis. Moreover, non-age-specific proteins (histatin-1 and BPI fold-containing family B member 1) were verified to be important candidate biomarkers for common dental caries.ConclusionsOur proteomic analysis performed using the discovery-through-verification pipeline revealed distinct variations caused by age factor in both healthy and cariogenic salivary proteomes, highlighting the significance of age in the great potential of saliva for caries diagnosis and biomarker discovery.Electronic supplementary materialThe online version of this article (10.1186/s12967-018-1669-2) contains supplementary material, which is available to authorized users.

The oral microbiome and salivary proteins influence caries in children aged 6 to 8 years

“…Next-generation sequencing technologies have been successfully applied in oral microbial analysis [ 12 – 14 ]. The isobaric tags for relative and absolute quantitation (iTRAQ) is a new technique which uses isotopes to label polypeptides for comparing proteomes quantitatively [ 15 , 16 ]. To the best of our knowledge, previous studies of caries-related microbiome and proteome were detached.…”

The secretory senescence of the senses of smell and taste

“…As concerns the organic components, in addition to the salivary concentration, they also measured the total amount secreted into the oral cavity, concluding that in the elderly the total values of most salivary components decrease parallel to the salivary flow rate 22 . In 2014, Nassar et al found a decrease in salivary calcium level in elderly people compared to young 23 . Conversely, Sevon et al reported elevated levels of salivary calcium in elderly women, with a peak at around the age of 50 years, compared to that of young women.…”

“…On the other hand, in their 2014 study Nassar et al assessed that the salivary buffering capacity is not related to age. As most of the salivary bicarbonate is secreted by the parotid gland, the parotid gland function seems to be not prejudiced by aging 23 . A lower salivary concentration of basic fibroblast growth factor (bFGF) has been reported in elderly subjects.…”

Protein Expression Profile in Rat Silicosis Model Reveals Upregulation of PTPN2 and Its Inhibitory Effect on Epithelial-Mesenchymal Transition by Dephosphorylation of STAT3

“…With the rapid development of proteomics technology and the application of high resolution mass spectrometry, isobaric tags for relative and absolute quantification (iTRAQ) is currently the most widely used technology in quantitative proteomics [6]. The core principle of iTRAQ is polypeptide labeling and quantification, which resolves quantitative changes in protein intensities with high sensitivity, accuracy, and reproducibility [7]; it is widely used in protein biomarker validation to support preclinical and clinical studies [8].In a previous iTRAQ technology study of silicosis, researchers employed SiO 2 to stimulate raw264.7 cells [9], and TGF-β to stimulate lung fibroblasts [10].…”