Patterns and variability in electrophoretic polypeptide profiles of human saliva in a healthy population

Cystatin SN (CST1) as a Novel Salivary Biomarker of Periodontitis

Identification of biomarkers could help in assessing periodontal health status and monitoring treatment outcomes. Therefore, the aim of this cross-sectional study was to identify potential innovative salivary biomarkers for the diagnosis of periodontitis using an untargeted proteomic approach. Forty-five healthy non-smoker participants diagnosed as having periodontally healthy conditions (H), severe periodontitis (P), and healthy but reduced periodontium after active periodontal treatment (T) were consecutively enrolled (15 per each group) in the study. A higher number of spots were identified in the proteome of unstimulated whole saliva collected from H and T subjects compared with P group, mainly within the range of 8-40 kDa. Protein spots of interest were analysed by MALDI-TOF-MS, allowing the identification of cystatin SN (CST1) isoform, as confirmed by Western blot. CST1 was markedly expressed in the H group, while it was absent in most P samples (p < 0.001). Interestingly, a distinct CST1 expression was observed in saliva from T patients. CST1 was negatively correlated with the percentage of pathological sites (p < 0.001) and was effective in discriminating active periodontitis from healthy periodontal status (whether H or T). Therefore, salivary CST1 may be a promising non-invasive biomarker for periodontal disease diagnosis and monitoring.

The "Ins and Outs" of Prostate Specific Membrane Antigen (PSMA) as Specific Target in Prostate Cancer Therapy

Prostate-specific membrane antigen (PSMA) is expressed in epithelial cells of the prostate gland and is strongly upregulated in prostatic adenocarcinoma, with elevated expression correlating with metastasis, progression, and androgen independence. Because of its specificity, PSMA is a major target of prostate cancer therapy; however, detectable levels of PSMA are also found in other tissues, especially in salivary glands and kidney, generating bystander damage of these tissues. Antibody target therapy has been used with relative success in reducing tumor growth and prostate specific antigen (PSA) levels. However, since antibodies are highly stable in plasma, they have prolonged time in circulation and accumulate in organs with an affinity for antibodies such as bone marrow. For that reason, a second generation of PSMA targeted therapeutic agents has been developed. Small molecules and minibodies have had promising clinical trial results, but concerns about their specificity had arisen with side effects due to accumulation in salivary glands and kidneys. Herein we study the specificity of small molecules and minibodies that are currently being clinically tested. We observed a high affinity of these molecules for PSMA in prostate, kidney and salivary gland, suggesting that their effect is not prostate specific. The search for specific prostate target agents must continue so as to optimally treat patients with prostate cancer, while minimizing deleterious effects in other PSMA expressing tissues.

Wine pH Prevails over Buffering Capacity of Human Saliva

Wine is an acidic beverage; its pH (2.9-3.8) is critically important to its organoleptic properties. During degustation, wine interacts with <1 mL of mouth saliva, the pH of which is near 7.0. This is buffered predominantly by the carbonate/bicarbonate pair (pK_a = 6.1). Few data are available on whether the buffering capacity of saliva may alter the pH of wine and thus its sensorial properties. In this study both in vitro and in vivo approaches were conducted to measure pH in mixtures of representative red and white wines with human saliva. Continuous additions of microvolumes of either wine to a definite volume (3 mL) of saliva in vitro resulted in a progressive and steep decline in the pH of the wine/saliva mixture. Thus, a few microliters of either wine (<0.27 mL) was sufficient to reduce the pH of saliva by 1 pH unit. Further additions of wine to saliva lowered the pH to that of the corresponding wine. In the in vivo assay, definite volumes (1.5-18 mL) of either wine were mixed for 15 s with the mouth saliva of individual healthy subjects before pH determination in the expectorated wine/saliva mixtures. Compared to saliva, pronounced decreases in pH were observed, thus approaching the pH of wine even with the smallest volume of wine in the assay. Altogether, these results demonstrate that the buffering capacity of wine prevails over that of saliva and that during degustation the pH of the wine/saliva mixture in the mouth is, at least temporarily, that of the corresponding wine.

Quantitative analysis of the intra- and inter-subject variability of the whole salivary proteome

BACKGROUND AND OBJECTIVE

Interest in human saliva is increasing for disease-specific biomarker discovery studies. However, protein composition of whole saliva can grossly vary with physiological and environmental factors over time and it comprises human as well as bacterial proteins.

MATERIAL AND METHODS

We compared intra- and inter-subject variabilities using complementary gel-based (two-dimensional difference gel electrophoresis, 2-D DIGE) and gel-free (liquid chromatography tandem mass spectrometry, LC-MS/MS) proteomics profiling of saliva. Unstimulated whole saliva of four subjects was examined at three different time-points (08.00 h, 12.00 h and 17.00 h) and variability of the saliva proteome was analyzed on two successive days by LC-MS/MS.

RESULTS

In the 2-D DIGE experiment, the median coefficient of variation (CV) for intra-subject variability was significantly lower (CV of 0.39) than that for inter-subject variability (CV of 0.57; CV of technical replicates 0.17). LC-MS/MS data confirmed the significantly lower variation within subjects over time (CV of 0.37) than the inter-subject variability (CV of 0.53; CV of technical replicates 0.11), and that the inter-subject variability was not time-dependent.

CONCLUSION

Both techniques revealed similar trends of variations on technical, intra- and inter-subject level but provided peptide and protein focused information and should thus be used as complementary approaches. The data presented indicate that 2-D DIGE as well as LC-MS/MS approaches are suitable for biomarker screening in saliva.

Enhancement of both salivary protein-enological tannin interactions and astringency perception by ethanol

Red wine astringency has been associated with interactions of tannins with salivary proteins. Tannins are active protein precipitants. Not much evidence exists demonstrating contribution of other wine components to astringency. We aimed to investigate an eventual role of ethanol both in astringency and salivary protein-enological tannin interactions. A trained sensory panel scored perceived astringency. Salivary protein-tannin interactions were assessed by observing both tannin-dependent changes in salivary protein diffusion on cellulose membranes and tannin-induced salivary protein precipitation. Proanthocyanidins and gallotannins in aqueous and hydroalcoholic solutions were assayed. A biphasic mode of diffusion on cellulose membranes displayed by salivary proteins was unaffected after dilution with water or enological concentrations of ethanol. At those concentrations ethanol was not astringent. In aqueous solution, tannins provoked both restriction of salivary protein diffusion, protein precipitation, and astringency. Those effects were exacerbated by 13% ethanol. In summary, enological concentrations of ethanol exacerbate astringency and salivary protein-tannin interactions.