The proteomic profile of whole and glandular saliva in healthy pain-free subjects

High similarity of IgG antibody profiles in blood and saliva opens opportunities for saliva based serology

Saliva based diagnostics is a rapidly evolving field due to the large diagnostic potential and simple sample collection. Currently only few individual molecules were investigated for their diagnostic capabilities in saliva. A systematic comparison of IgG antibody profiles in saliva and plasma is still missing in scientific literature. Our hypothesis is that IgG profiles in plasma and saliva are highly similar for each individual. As a consequence, one could implement practically any plasma based IgG assay (classical serology) as saliva based assay. In other words, the IgG antibodies found in blood are also accessible from saliva. We confirm our hypothesis by comparing IgG reactivities towards protein and peptide antigens. We isolated saliva IgG with high purity and demonstrate that plasma IgG reactivities (classical serology) can be inferred from saliva. As a showcase we perform Hepatitis B virus antibody (plasma-)titer determination from saliva. Additionally we show that plasma and saliva IgG profiles of 20 individuals are highly similar for 256 peptide antigens and match (unsupervised) with high probabilities. Finally, we argue for generalisation to the complete IgG antibody profile. The presented findings could contribute greatly to the development of saliva based diagnostic methods of numerous antibody based tests.

Tumor-Derived Extracellular Vesicles as a Novel Source of Protein Biomarkers for Cancer Diagnosis and Monitoring

"Liquid biopsies" have received attention as a complementary tool for traditional tissue biopsies that may enhance the spectrum of analysis for tumor-derived factors. One such factor gaining prominence in the liquid biopsy field is extracellular vesicles (EVs), membrane-bound nanovesicles which are secreted by cells into biofluids such as blood, urine, and saliva. EVs are released in both physiological and pathological conditions and can transport a variety of molecules, including proteins, metabolites, RNA, microRNAs, and DNA, to distant sites throughout the body. As such, they are emerging as a promising source of tumor biomarkers for the noninvasive diagnosis, prognosis, and monitoring of cancer patients. In particular, the wealth of tumor-related information that can be gleaned from the EV proteomic cargo has become apparent through mass spectrometric analysis, which has provided new benchmarks for clinically focused biomarker research. In this review, the current achievements in the use of MS for identifying potential EV-derived protein biomarkers of cancer are explored, and the techniques and challenges involved in this pursuit are summarized.

Salivary beta-endorphin and substance P are not biomarkers of neuropathic chronic pain propensity

Objective

The pathophysiology of chronic pain is complex, with most of our knowledge being derived from preclinical studies. The search for biomarkers mirroring the pathophysiology of chronic pain is ongoing, and there is an increasing interest in saliva as a diagnostic tool. Given what is known about salivary substance P and salivary gland innervation, we hypothesized that salivary substance P and/or beta-endorphin might reflect the basal activity of these neuropeptides in the central nervous system, thereby perhaps mirroring a general propensity to chronic pain. Based on this overall hypothesis, our aim was to compare salivary levels of these neuropeptides in chronic neuropathic pain patients with healthy controls. An additional aim was to relate salivary levels to plasma levels.

Materials and methods

We compared salivary concentrations of beta-endorphin and substance P in 14 chronic neuropathic pain patients with concentrations in 18 healthy controls using a Luminex technology kit. Salivary-to-plasma quotients were also calculated.

Results

We found no significant difference between the groups' salivary concentrations of substance P and beta-endorphin. No correlation was found between salivary and plasma concentrations of each neuropeptide, which we hypothesize might point to local production of beta-endorphin and/or substance P in the salivary glands. Given high substance P salivary-to-plasma quotients, such a local production seems more likely for substance P than for beta-endorphin.

Conclusions

Propensity to neuropathic chronic pain was not substantiated by our analysis of salivary levels of substance P and/or beta-endorphin. However, we report salivary-to-plasma quotients that give potentially important physiological insight about these neuropeptides.

No association of salivary total tau concentration with Alzheimer's disease

There is a need for an accessible biomarker that can complement current cerebrospinal fluid and imaging biomarkers in an accurate and early diagnosis of Alzheimer disease (AD). Saliva is a rich source of potential biomarkers and proteins related to neurodegenerative disorders have been shown to be present in this matrix, including tau. In this study, we quantified salivary total tau (t-tau) concentration in 160 healthy elderly control, 68 mild cognitive impairment, and 53 AD participants using ultrasensitive Single molecule array (Simoa) technology. No median difference in salivary t-tau concentration was found between AD and mild cognitive impairment or healthy elderly control (12.3 ng/L, 9.8 ng/L and 9.6 ng/L, respectively, p = 0.219). In addition, there was no association of salivary t-tau concentration with neurophysiological assessment or structural magnetic resonance imaging. Despite a nominal increase in AD, due to the large overlaps in concentrations between clinical groups, we conclude that salivary t-tau is a suitable biomarker neither for AD nor for cognitive impairment.

Standardization of a protocol for shotgun proteomic analysis of saliva

INTRODUCTION

Saliva contains numerous proteins and peptides, each of them carries a number of biological functions that are very important in maintaining the oral cavity health and also yields information about both local and systemic diseases. Currently, proteomic analysis is the basis for large-scale identification of these proteins and discovery of new biomarkers for distinct diseases.

OBJECTIVE

This study compared methodologies to extract salivary proteins for proteomic analysis.

MATERIAL AND METHODS

Saliva samples were collected from 10 healthy volunteers. In the first test, the necessity for using an albumin and IgG depletion column was evaluated, employing pooled samples from the 10 volunteers. In the second test, the analysis of the pooled samples was compared with individual analysis of one sample. Salivary proteins were extracted and processed for analysis by LC-ESI-MS/MS.

RESULTS

In the first test, we identified only 35 proteins using the albumin and IgG depletion column, while we identified 248 proteins without using the column. In the second test, the pooled sample identified 212 proteins, such as carbonic anhydrase 6, cystatin isoforms, histatins 1 and 3, lysozyme C, mucin 7, protein S100A8 and S100A9, and statherin, while individual analysis identified 239 proteins, among which are carbonic anhydrase 6, cystatin isoforms, histatin 1 and 3, lactotransferrin, lyzozyme C, mucin 7, protein S100A8 and S100A9, serotransferrin, and statherin.

CONCLUSIONS

The standardization of protocol for salivary proteomic analysis was satisfactory, since the identification detected typical salivary proteins, among others. The results indicate that using the column for depletion of albumin and IgG is not necessary and that performing individual analysis of saliva samples is possible.

Saliva as a medium to detect and measure biomarkers related to pain

Saliva is often neglected as a body fluid of diagnostic or prognostic value, even though generally well accepted by the patients. This is due to lack of a standardized collection procedure. The aim of this study was to identify the ideal saliva collection technique and develop new sensitive methods to detect and analyse markers related to pain in healthy pain-free subjects. Plasma and five different saliva collection approached was evaluated during strictly controlled conditions. Levels of nerve growth factor (NGF), calcitonin gene-related peptide (CGRP) and brain derived neurotropic factor (BDNF) were determined using novel western blotting based technology. Glutamate and substance P (SP) was determined using commercial available methods. Several new isoforms were found for NGF, CGRP and BDNF in saliva. The isoform pattern showed significant variation in both expression and chemiluminescence levels between different collection methods. New sensitive methods to study pain related markers in saliva were developed in this study. Furthermore, we are first to demonstrate a correlation between the Glutamate concentration in stimulated whole saliva and blood. However, the fundamental conclusion drawn is the importance of consistency in the collection method.

Evaluation of the difference in caries experience in diabetic and non-diabetic children-A case control study

Aim

To evaluate the caries prevalence and related variables in Type 1 diabetic and non-diabetic children and among the diabetic children according to their metabolic status.

Methods

Sixty-eight diabetic and 136 non-diabetic children, matching by gender and age (4–14 years) were enrolled. The diabetic children were divided: a) 20 children in good metabolic control (Hb1ac≤7.5) and b) 48 children in bad metabolic control (Hb1ac>7.5). Dietary and oral hygiene habits were investigated. Caries status was registered using the International Caries Detection and Assessment System. Oral microflora was analysed using the checkerboard DNA-DNA hybridisation method. Plaque acidogenicity was recorded after a sucrose rinse.

Results

Sugared beverage and snack intake was higher in diabetic group compared to non-diabetic group (p = 0.03 and p = 0.04, respectively) and in subjects in bad metabolic control (p = 0.03 and p<0.01, respectively). Oral hygiene habits were similar, except for the use of fluoridated adjuvants, higher in non-diabetic children (p = 0.04). No statistically significant differences were observed regarding caries figures, but a higher number of caries free subjects was found in diabetic subjects in good metabolic control (p<0.01). Significant difference for the main cariogenic bacteria was found between diabetic and non-diabetic subjects (p<0.05). The pH values showed statistically significant differences between diabetic and non-diabetic subjects and between diabetic subjects in good and bad metabolic control (p<0.01).

Conclusions

Diabetic children in good metabolic control might even be considered at low caries risk, while those in bad metabolic control showed an oral environment prone to a high caries risk.

Salivary cytokine levels in early gingival inflammation

Salivary protein levels have been studied in periodontitis. However, there is lack of information on salivary cytokine levels in early gingival inflammation. The aim of this study was to determine salivary levels of vascular endothelial growth factor (VEGF), interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, IL-1β, and IL-1 receptor antagonist (IL-1Ra) in gingival inflammation. Twenty-eight systemically and orally healthy nonsmokers abstained from oral hygiene protocols for 10 days. After that, self-performed cleaning was resumed for 14 days. Plaque and gingival indexes were measured, and saliva samples were collected at days 1, 4, 7, 10, and 24. Salivary cytokines were detected with Luminex®-xMAP™. Salivary IL-1β, IL-1Ra, and VEGF levels decreased after 10 days' development of experimental gingivitis and reached baseline levels at the end of the 2-week resolution period. Salivary IL-8 levels decreased and remained low during development and resolution of experimental gingivitis. Initial inflammation in gingival tissues is associated with a decrease in inflammatory cytokines in saliva. Further studies are needed to evaluate if inflammatory cytokines bind to their functional receptors within the gingival tissue during early gingivitis, which may limits their spillover to the gingival crevice and ultimately saliva.