Clinical applications of electrophoresis of human salivary proteins

Sarcoidosis and Sjögren's syndrome: clinical and salivary evaluation

BACKGROUND

Sarcoidosis and Sjögren's syndrome are two different diseases; however, when affecting the salivary glands, both diseases exhibit similar clinical signs and symptoms, which often complicates the diagnosis. The purpose of this study was to investigate the possibility of using salivary electrophoresis to differentiate between the two diseases.

METHODS

Saliva was collected from patients with sarcoidosis and patients with Sjögren's syndrome. Salivary flow rate, total protein, and electrophoretic profiles were examined.

RESULTS

Mean salivary flow rate was 0.41 ± 0.07 ml/min/gland vs. 0.43 ± 0.07 ml/min/gland; total salivary protein was 130.0 ± 29.2 mg% vs. 104.0 ± 8.8 mg% for sarcoidosis vs. Sjögren's syndrome, respectively. No differences were observed in salivary flow rate, total salivary protein, or electrophoretic profile between patients with sarcoidosis and patients with Sjögren's syndrome (P = 0.768, 0.718, and 1.000, respectively).

CONCLUSIONS

Salivary protein electrophoresis does not appear to be useful to differentiate between sarcoidosis and Sjögren's syndrome.

Salivary proteins and early childhood caries: A gel electrophoretic analysis

BACKGROUND

Early childhood caries (ECC) is a common disease process that afflicts a large proportion of the child population worldwide. Extensive research in past indicates that it is the result of bacterial infection, also influenced by host and dietary factors. Current caries research seeks to identify risk factors as well as natural oral defenses that may protect against or prevent caries development. Saliva, in spite of being the strongest defense system, still has a wide array of properties and proteins whose role is yet not clearly known.

AIM

To compare the resting human whole salivary characteristics in children with ECC and those who are caries free.

SETTINGS AND DESIGN

The study was conducted over a period of 9 months in 4- to 6-year-old 100 children comprising two groups - 50 with ECC and 50 caries free.

MATERIALS AND METHODS

The whole salivary flow rate, pH, mean protein concentration, and the electrophoretic profile of salivary proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were compared among both groups.

STATISTICAL ANALYSIS

The SPSS (version 11.0) software package was used to conduct the chi-square, Fisher's exact and Pearson's chi-square tests to compare the data.

RESULTS

On gel electrophoresis, there was a significant difference among both groups with caries-free subjects having a higher number of proline-rich protein bands, substantiating the protective role of this protein. A significantly higher number of glycoprotein bands were observed in the whole saliva of subjects with ECC. A significant inverse correlation between the mean protein concentration and the whole salivary flow rate was observed in both groups.

Influence of the glycosylation of human salivary proline-rich proteins on their interactions with condensed tannins

Binding of condensed tannins to salivary proteins is supposed to be involved in their astringency. First, complexes arising from the interaction of saliva from two individuals and tannins were studied. Then interaction mixture models containing purified saliva proteins were developed. The highest polymerized tannins predominantly precipitated together with the salivary proteins. Electrophoresis of proteins in combination with thiolysis analysis of tannins indicated proline-rich protein (PRP)-polyphenol complexes in precipitated fractions and also in the soluble ones with individual differences. Individual salivas exhibiting different protein patterns were discriminated with regard to their ability to interact with tannins. From binding studies with purified classes of salivary proteins, interactions were shown to depend on the nature of the protein, in particular on their glycosylation state. For low concentrations of tannins, glycosylated PRP-tannin interactions led to complexes that remained soluble, whereas those arising from nonglycosylated PRP-tannin interactions were precipitated. This finding could indicate that under physiological conditions, complexes involving glycosylated proteins maintain part of the lubrication of the oral cavity, whereas tannin trapping leads to a lower astringency perception.

Analysis of the human saliva proteome

Interest in the characterization of the salivary proteome has increased in the last few years. This review discusses the different techniques and methodologies applied to the separation and identification of salivary proteins. Nowadays, proteomic techniques are the state of the art for the analysis of biologic materials and saliva is no exception. 2D electrophoresis and tryptic digest analysis by mass spectrometry are the typical methodology, but new approaches using 2D liquid chromatography/mass spectrometry methods have already been introduced for saliva analysis. Due to their important physiologic role in the oral cavity, low-molecular-weight proteins and peptides are also included in this article and the methodologies discussed.

Peptide mapping of proteins in human body fluids using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Human body fluids have been rediscovered in the post-genomic era as great sources of biological markers and perhaps particularly as sources of potential protein biomarkers of disease. Analytical tools that allow rapid screening, low sample consumption, and accurate protein identification are of great importance in studies of complex biological samples and clinical diagnosis. Mass spectrometry is today one of the most important analytical tools with applications in a wide variety of fields. One of the fastest growing applications is in proteomics, or the study of protein expression in an organism. Mass spectrometry has been used to find post-translational modifications and to identify key functions of proteins in the human body. In this study, we review the use of human body fluids as sources for clinical markers and present new data that show the ability of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) to identify and characterize proteins in four human body fluids: plasma, cerebrospinal fluid (CSF), saliva, and urine. The body fluids were tryptically digested without any prior separation, purification, or selection, and the digest was introduced into a 9.4 T FTICR mass spectrometer by direct-infusion electrospray ionization (ESI). Even though these samples represent complex biological mixtures, the described method provides information that is comparable with traditional 2D-PAGE data. The sample consumption is extremely low, a few microliters, and the analysis time is only a few minutes. It is, however, evident that the separation of proteins and/or peptides must be included in the methodology, in order to detect low-abundance proteins and other proteins of biological relevance.

Determination of the human salivary peptides histatins 1, 3, 5 and statherin by high-performance liquid chromatography and by diode-array detection

A reversed-phase high-performance liquid chromatography (HPLC) method with diode-array detection for the quantification of several human salivary peptides is described. Sample pretreatment consisted of the acidification of whole saliva by phosphate buffer. This treatment produced precipitation of mucins, alpha-amylases and other high-molecular-mass salivary proteins, simultaneous inhibition of intrinsic protease activities and reduction of sample viscosity. Direct HPLC analysis by diode-array detection of the resulting acidic sample allowed one to quantify histatin 1, histatin 3, histatin 5, statherin, as well as uric acid, in normal subjects. Moreover, the groups of peaks pertaining to proline-rich proteins and cystatins were tentatively identified. The method can be useful in assessing the concentration of salivary peptides from normal subjects and from patients suffering oral and/or periodontal diseases.

Xerostomia and hyposalivation

Dry mouth must not be considered a trivial problem in the population, since it constitutes a phenomenon with many aspects relative to oral function as well as quality of life. Up until today, no global consensus has been reached with regard to the terminology of dry mouth, creating a substantial problem for research, education, diagnosis, and therapy. In this report, salivary gland hypofunction has been selected as the overarching term for subjective symptoms and objective signs of dry mouth. Its different aspects--xerostomia, hyposalivation, and altered saliva composition--are reviewed with respect to prevalence, diagnosis, and etiology. It is concluded that these aspects of salivary gland hypofunction are separate entities, which in many respects are interrelated, constituting not merely a dental but also a medical and social concern.

Salivary electrophoresis in the diagnosis of Sjögren's syndrome

OBJECTIVE

The purpose of this study was to investigate the potential use of salivary electrophoresis for the diagnosis of Sjögren's syndrome.

METHODS

Salivary protein profiles of 43 patients and 39 healthy control subjects were compared on three different gel electrophoresis systems: sodium dodecylsulfate-polyacrylamide gel electrophoresis, anionic polyacrylamide gel electrophoresis, and immobilized pH gradient gel electrophoresis (isoelectric point, 3.5-5.0).

RESULTS

Most of the patients with Sjögren's syndrome exhibited an electrophoretic profile that was different from that of the healthy control subjects. Among the three gel electrophoresis systems examined, the immobilized pH gradient system appeared to be the most reliable for Sjögren's syndrome. Tests of accuracy revealed that the immobilized pH gradient system exhibits high specificity (97%), sensitivity (95%), positive predictive value (97%), and negative predictive value (95%) in the diagnosis of Sjögren's syndrome.

CONCLUSIONS

Our results suggest that salivary electrophoresis is a potentially useful test for the diagnosis of Sjögren's syndrome.

Human glandular salivas: their separate collection and analysis

Human saliva is secreted by the three pairs of major salivary glands (parotid, submandibular, and sublingual), and numerous minor ones, e.g. labial, buccal and (glosso)palatine glands. Using individually adapted collection devices, sublingual, submandibular, parotid and palatine secretions of five individuals were collected and analyzed. Electrophoretic analysis revealed that each type of saliva possesses characteristic features, despite interindividual variations. Parotid salivas are characterized by intensely staining amylase and proline-rich protein bands, but contain minute amounts of cystatins, lysozyme and the extra-parotid glycoprotein. Sublingual salivas are characterized by high concentrations of both types of salivary mucins, MG1 and MG2, and contain relatively high levels of lysozyme. Submandibular salivas contain highest concentration of salivary cystatin S. Palatine secretions contain high molecular weight mucins and a relatively high amylase concentration.

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of human whole saliva

The purpose of this study was to characterize the electrophoretic patterns of human resting and stimulated whole saliva. Pooled and individual, uncentrifuged, unprocessed whole saliva from 20 healthy, unmedicated individuals was run on sodium dodecyl sulphate-polyacrylamide gel electrophoresis and stained with Coomassie blue R-250. Similar and characteristic patterns for whole saliva were observed for all samples, consisting of over 34 blue- and pink-violet-staining bands. Individual differences were usually in the size (or density) of the bands, not in the number. Repeat sampling of stimulated whole saliva over a period of weeks from the same individuals revealed a striking consistency of protein patterns, indicating a profound physiological stability of whole saliva. These results provide baseline data for whole saliva and suggest its use for future studies.

Electrophoretic analysis of stimulated cat parotid saliva

The proteins of parasympathetically stimulated cat parotid saliva were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and high resolution two-dimensional electrophoresis (2-DE). SDS-PAGE revealed up to 30 polypeptide bands in microliter volumes of unconcentrated saliva. The patterns were highly reproducible and characterized by prominent bands of M(r) 57,000, M(r) 30,000 and M(r) 15,000. The major protein (M(r) 30,000) appeared as a dimer (M(r) 60,000) when electrophoresed under non-reducing conditions but dissociated into its monomeric form when the SDS concentration of the denatured samples was increased from 1 to 5%. This indicates a noncovalent association. The protein patterns of saliva from different cats differed slightly but sequential samples from the same cat (collected during 90 min of stimulation) showed little change in protein pattern apart from a fall in total protein content. Following 2-DE, the major protein (M(r) 30,000) appeared as a complex array of at least eight spots in two tiers (pI 5.2-6.2; M(r) 28,000 and 32,000). The characteristics of this protein are discussed with reference to allergy to cats.

Sodium dodecyl sulfate-capillary gel electrophoresis of proteins using non-cross-linked polyacrylamide

Proteins with relative molecular masses of 14,000 to 205,000 were separated by sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) using non-cross-linked linear polyacrylamide gels on both coated and uncoated fused-silica capillaries. It was determined that viscosity of the acrylamide solution was a major factor affecting column stability with linear acrylamide gels. When the viscosity of the acrylamide solution reaches 100 cP, electro-osmotically driven displacement of the gels is insignificant. Uncoated capillaries provided better resolution, stability, and reproducibility than surface coated capillaries when the concentration of linear polyacrylamide was greater than 4%. At lower gel concentrations, non-cross-linked polyacrylamide is easily displaced from the columns. A calibration plot of log molecular mass vs. mobility with non-linear polyacrylamide was linear, which indicated that resolution was equivalent to that obtained with cross-linked acrylamide. Separations with model proteins indicated that baseline resolution between protein species that vary 10% in molecular mass can be achieved.

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of human parotid salivary proteins

The proteins in human parotid saliva have been separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis into 20 or more well resolved species. The Coomassie Brilliant Blue (CBB) R-250 and silver staining procedures have been modified to overcome the problems encountered with staining of proline-rich proteins. By means of the CBB R-250 procedure which stains proline-rich proteins pink-violet, immunoblotting, concanavalin A binding, periodate-Schiff staining and zinc binding, all of the major proteins have been characterised. Substantial individual-to-individual differences were observed in the protein patterns formed. Comparison of parotid, submandibular, and whole saliva from a single individual indicated that fewer proline-rich proteins are expressed in submandibular saliva than in parotid, but whole saliva contains much lower levels than either duct secretion. The results will form a useful base for future research into the functions of salivary proteins.