Salivary Proteins May Be Useful for Determining Caries Susceptibility

Mucin O-glycans suppress quorum-sensing pathways and genetic transformation in Streptococcus mutans

Mucus barriers accommodate trillions of microorganisms throughout the human body while preventing pathogenic colonization¹. In the oral cavity, saliva containing the mucins MUC5B and MUC7 forms a pellicle that coats the soft tissue and teeth to prevent infection by oral pathogens, such as Streptococcus mutans². Salivary mucin can interact directly with microorganisms through selective agglutinin activity and bacterial binding^2-4, but the extent and basis of the protective functions of saliva are not well understood. Here, using an ex vivo saliva model, we identify that MUC5B is an inhibitor of microbial virulence. Specifically, we find that natively purified MUC5B downregulates the expression of quorum-sensing pathways activated by the competence stimulating peptide and the sigX-inducing peptide⁵. Furthermore, MUC5B prevents the acquisition of antimicrobial resistance through natural genetic transformation, a process that is activated through quorum sensing. Our data reveal that the effect of MUC5B is mediated by its associated O-linked glycans, which are potent suppressors of quorum sensing and genetic transformation, even when removed from the mucin backbone. Together, these results present mucin O-glycans as a host strategy for domesticating potentially pathogenic microorganisms without killing them.

Saliva and Gingival Crevicular Fluid (GCF) Collection for Biomarker Screening

Assaying different biological markers (biomarkers) is commonly used to monitor health status and aid in the diagnosis of diseases. With the recent advances in highly sensitive protein assays, whole saliva (WS) and gingival crevicular fluid (GCF) appear to be fluids that may contain important biomarkers with various applications in dentistry and medicine. Herein, we describe the process of GCF and WS sample collection and preparation for assaying clinically relevant biomarkers in clinical screening trials. Analysis of biomarkers in WS and GCF represents an easy and practical approach for the diagnosis and screening of different pathological conditions particularly in epidemiological surveys.

Revealing the Amylase Interactome in Whole Saliva Using Proteomic Approaches

Understanding proteins present in saliva and their function when isolated is not enough to describe their real role in the mouth. Due to protein-protein interactions, structural changes may occur in macromolecules leading to functional modulation or modification. Besides amylase's function in carbohydrate breakdown, amylase can delay proteolytic degradation of protein partners (e.g., histatin 1) when complexed. Due to its biochemical characteristics and high abundance in saliva, amylase probably interacts with several proteins acting as a biological carrier. This study focused on identifying interactions between amylase and other proteins found in whole saliva (WS) using proteomic approaches. Affinity chromatography was used, followed by gel electrophoresis methods, sodium dodecyl sulfate and native, tryptic in-solution and in-gel digestion, and mass spectrometry. We identified 66 proteins that interact with amylase in WS. Characterization of the identified proteins suggests that acidic (pI < 6.8) and low molecular weight (MW < 56 kDa) proteins have preference during amylase complex formation. Most of the identified proteins present biological functions related to host protection. A new protein-amylase network was constructed using the STRING database. Further studies are necessary to investigate individualities of the identified amylase interactors. These observations open avenues for more comprehensive studies on not yet fully characterized biological function of amylase.

Relationship among α amylase and carbonic anhydrase VI in saliva, visible biofilm, and early childhood caries: a longitudinal study

AIM

This longitudinal study investigated the relationship among early childhood caries (ECC), α amylase, carbonic anhydrase VI (CA VI), and the presence of visible biofilm, besides detecting if these variables could predict risk for ECC.

DESIGN

One hundred children were divided into two groups: caries group (n = 45) and caries-free group (n = 55). Visible biofilm on maxillary incisors was recorded, followed by caries diagnosis in preschoolers at baseline and at follow-up. Saliva samples were collected, and activities of CA VI and α amylase were determined. Data normality was assessed by Shapiro-Wilk test and then Mann-Whitney, Spearman correlation, and chi-square tests followed by multiple logistic regression analysis (α = 0.05, 95% confidence interval).

RESULTS

CA VI activity was significantly higher in saliva of children with caries (P ≤ 0.05), and α amylase activity was significantly higher in saliva of caries-free children (P < 0.0001). Children with α amylase activity in saliva lower than 122.8 U/mL (OR = 3.33 P = 0.042) and visible biofilm on maxillary incisors (OR = 3.6 P = 0.009) were more likely to develop ECC than caries-free children. A negative correlation between caries and α amylase activity was found (P = 0.0008).

CONCLUSIONS

The presence of visible biofilm and low salivary activity of α amylase may be considered risk predictors for ECC.

Saliva and biofilm-based diagnostics: a critical review of the literature concerning sialochemistry

There is some evidence to support the use of salivary diagnostics in dentistry.

BACKGROUND AND PURPOSE

The use of saliva as a diagnostic fluid has the potential to shape the role of oral health care professionals in the health care system. While more than a handful of chairside diagnostic tests are available for use by private practitioners, the evidence supporting their use continues to emerge.

METHODS

An electronic search of the literature indexed on the PubMed electronic database was conducted to identify human clinical trials utilizing commercially available salivary diagnostics. Papers meeting the inclusion criteria, and any applicable references were critically appraised following SORT guidelines.

CONCLUSIONS

While the literature concerning salivary analysis is continuously growing, the limited literature that is available doesn't focus on patient oriented health outcomes. This 'infant' literature is focused on validating metrics and identifying biomarkers with diagnostic potential. As such, the evidence level of the literature is graded as level 3. Despite the lower grade, the research in this area shows consistent results, coherent conclusions, and research identifying new biomarkers will provide additional dimensions to salivary diagnostics.