Two-dimensional electrophoresis of human salivary proteins from patients with sialoadenopathy

Chemosensate-Induced Modulation of the Salivary Proteome and Metabolome Alters the Sensory Perception of Salt Taste and Odor-Active Thiols

Oral stimulation with chemosensates was found to trigger changes in the composition of the salivary proteome and metabolome, which translate into a functional modulation of odor and taste perception. Orosensory intervention with 6-gingerol induced a significant increase in the abundance of salivary sulfhydryl oxidase 1, which was found to catalyze the oxidative decline of odor-active 2-furfurylthiol, thus resulting in a decrease in the odorant levels in exhaled breath, as shown by PTR-MS, and a reduction of the perceived sulfury after-smell. Therefore, sulfhydryl oxidase 1 may be considered as a component of a molecular network triggering oral cleansing mechanisms after food ingestion. Moreover, oral stimulation with citric acid, followed by targeted metabolomics, was found to induce a strong increase in salivary concentrations of minerals and, in particular, sodium ions, whereas the other metabolites were rather unaffected. Because of the elevated basal levels of salivary sodium after citric acid stimulation, NaCl test stimuli were perceived as significantly less salty, most likely due to the decreased sensory contrast. This indicates the modulation of the salivary proteome and metabolome to be a major perireceptor event in fine-tuning odor and taste sensitivity.

Dynamic Proteome Alteration and Functional Modulation of Human Saliva Induced by Dietary Chemosensory Stimuli

Saliva flow measurements and SDS-PAGE separation of human whole saliva freshly collected after oral stimulation with citric acid (sour), aspartame (sweet), iso-α-acids (bitter), mono sodium l-glutamate (umami), NaCl (salty), 6-gingerol (pungent), hydroxy-α-sanshool (tingling), and hydroxy-β-sanshool (numbing), followed by tryptic digestion, nano-HPLC-MS/MS, and label-free protein quantitation demonstrated a stimulus- and time-dependent influence of the dietary chemosensates on salivation and the salivary proteome composition. Gene ontology enrichment analysis showed evidence for stimulus-induced alterations of the saliva proteome to boot an efficient molecular defense network of the oral cavity, e.g., 6-gingerol increased salivary lactoperoxidase activity, catalyzing the oxidation of thiocyanate to produce the antimicrobial and antifungal hypothiocyanate, from 0.37 ± 0.02 to 0.91 ± 0.05 mU/mL 45 s after stimulation. In comparison, oral citric acid stimulation induced an increase of myeloperoxidase activity, catalyzing the chloride oxidation to generate antimicrobial hypochloride in saliva, from 0.24 ± 0.04 to 0.70 ± 0.1 mU/mL as well as an increase of salivary levels of lysozyme, exhibiting antimicrobial activity on Gram-positive bacteria, from 6.0-10 to 100-150 μg/mL. Finally, microbial growth experiments clearly demonstrated for the first time that the increase of the salivary lysozyme abundance upon oral citric acid stimulation translates into an enhanced biological function, that is an almost complete growth inhibition of the two lysozyme-sensitive Gram-positive bacteria tested.

Orosensory stimulation effects on human saliva proteome

Saliva flow induced by 6-gingerol (pungent), hydroxy-α/β-sanshools (tingling), and citric acid (sour) was measured, and the time-dependent changes in the whole saliva proteome were analyzed by means of 2D-PAGE, followed by tryptic in-gel digestion and MALDI-TOF-MS peptide mass fingerprint analysis. The proteins showing significantly decreased abundance after oral 6-gingerol stimulation were identified as glutathione S-transferase P, the heat shock protein β-1, the heat shock 70 kDa protein 1, annexin A1, and cytoplasmic β-actin, whereas prolactin inducible proteins (PIP), short palate, lung and nasal epithelium carcinoma-associated protein 2 (SPLUNC2), zinc-α-2-glycoproteins (Zn-α-GP), and carbonic anhydrase VI (CAVI) were found with increased abundance. As the effects of this study were observed instantaneously upon stimulation, any proteome modulation is very likely to result from the release of proteins from preformed vesicles and not from de novo synthesis. The elevated levels of SPLUNC2, Zn-α-GP, and CAVI might be interpreted to trigger innate protective mechanisms in mucosal immunity and in nonimmune mucosal defense and might play an important role during the initial stage of inflammation.

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.

Proteome analysis of glandular parotid and submandibular-sublingual saliva in comparison to whole human saliva by two-dimensional gel electrophoresis

The secretions of the salivary parotid and submandibular-sublingual (SMSL) glands constitute the main part of whole human saliva (WS) in which proline-rich proteins (PRPs) and mucins represent dominant groups. Although proteome analysis had been performed on WS, no identification of PRPs or mucins by 2-DE and MS was achieved in WS and no comprehensive analysis of both glandular secretions is available so far. The aim of this study was to compare the protein map of WS to parotid and SMSL secretions for the display of PRPs and mucins. WS and glandular secretions were subjected to 2-DE and spots were analyzed by MALDI-MS. New components identified in WS were cyclophilin-B and prolyl-4-hydroxylase. Also acidic and basic PRPs as well as the proline-rich glycoprotein (PRG) could now be mapped in WS. Acidic PRPs were found equally in parotid and SMSL secretions, whereas basic PRPs and PRG were found primarily in parotid secretion. Salivary mucin MUC7 was identified in SMSL secretion. Thus, the more abundant proteins of WS can be explained mainly by mixed contributions of parotid and SMSL secretions with only few components remaining that may be derived from local sources in the oral cavity.

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.

Increase of transforming growth factor-beta 1 in gingival crevicular fluid during human orthodontic tooth movement

The purpose of this study was to identify and quantify transforming growth factor-beta 1 (TGF-beta 1) in human gingival crevicular fluid, and to investigate changes during orthodontic tooth movement. Twelve patients (mean age, 14.4 yr) participated. An upper canine of each patient having one treatment for distal movement served as the experimental tooth; the contralateral and antagonistic canines were used as controls. The gingival crevicular fluid around the experimental and two control teeth was taken from each participant immediately before activation, and at 1, 24 and 168 h after the initiation of tooth movement. TGF-beta 1 was determined by enzyme-linked immunosorbent assay. The concentration of TGF-beta 1 was significantly higher in the experimental group than in the controls at 24 h after the experiment had begun, whereas TGF-beta 1 remained at baseline throughout the experiment for the two control groups. The presence of TGF-beta 1 in the gingival crevicular fluid was also identified by Western blot analysis. These results suggest that TGF-beta 1 is associated with the bone remodelling that occurs during orthodontic tooth movement.

Transforming growth factor-alpha in human submandibular gland and saliva

A sensitive sandwich enzyme immunoassay (EIA) for transforming growth factor-alpha (TGF-alpha) utilizing a polyclonal antibody that recognizes limited epitopes of both human TGF-alpha and rat TGF-alpha in combination with a monoclonal anti-TGF-alpha IgG1 galactosidase conjugate was developed. This assay shows no cross-reactivity with human epidermal growth factor. We can quantify the TGF-alpha level in not only human TGF-alpha (detection limit: 1 pg/ml), but also rat TGF-alpha (detection limit: 10 pg/ml) by virtue of cross-reactivity. Employing this assay system, we demonstrated that TGF-alpha is present in both human submandibular glands and submandibular/sublingual saliva.

Salivary beta 2-microglobulin in NZB/WF1 mice

Unstimulated parotid and submandibular/sublingual saliva from New Zealand black/WF1 (NZB/WF1) mice as collected by microcapillary (1 microliter), and the content of beta 2-microglobulin (beta 2-MG) determined by a sandwich enzyme immunoassay. Salivary beta 2-MG contents of control C57BL/6 and NZB/WF1 mice (45 weeks of age) were 0.68 +/- 0.18 micrograms/ml and 1.42 +/- 0.21 micrograms/ml (mean +/- SD), respectively, from the parotid gland and 0.62 +/- 0.17 micrograms/ml and 1.34 +/- 0.21 microliters/ml, respectively, from the submandibular sublingual glands. However, the concentration of beta 2-MG was not increased in the NZB/WF1 mice at 5 and 20 weeks of age. Saliva from NZB/WF1 mice (45 weeks old) was fractionated by micro two-dimensional gel electrophoresis; it exhibited both qualitative and quantitative changes in protein composition in comparison to the two-dimensional at 5 weeks of age. These observations parallel those in saliva from patients with Sjögren's syndrome.

Increased beta 2-microglobulin in both parotid and submandibular/sublingual saliva from patients with Sjögren's syndrome

Samples of unstimulated saliva from patients with sialoadenopathy were collected by microcapillary tube (1 microliter), and their beta 2-microglobulin (B2-MG) content determined by a sandwich enzyme immunoassay. A higher than normal (control) concentration of the globulin was present in both parotid and submandibular/sublingual saliva from the patients with Sjögren's syndrome but not in the samples from the patients with sialoadenitis or diabetes mellitus. The increase in B2-MG in saliva from patients with Sjögren's syndrome may reflect that immunolopathological events are important in the degeneration of both glands in this disease. Therefore, the determination of B2-MG in saliva may be a simple, non-invasive technique for confirming the diagnosis of Sjögren's syndrome as an autoimmune disease.