Saliva contains a complex mixture of proteins and peptides as well as fragments derived from these molecules. By RP 1 -HPLC-ESI-MS analysis of the acidic soluble fraction of human whole saliva we have identified in the chromatographic pattern more than 120 different proteins and naturally occurring peptides (1-6). Their characterization was performed by a variety of mass spectrometric techniques coupled with different enzymatic treatments and amino acid sequencing. The proteins and naturally occurring peptides belong to families of well characterized salivary proteins including Histatins, Statherin, acidic and basic proline-rich proteins (aPRP and bPRP), Cystatins, and Defensins (1-6). Two-dimensional gel electrophoresis has also been used by other researchers for analysis of salivary proteins and peptides, but this technique is not well suited for identification of small peptides as illustrated by the difficulty in identifying Histatins and the majority of bPRPs and bPRP fragments (7-9). However, knowledge of salivary proteins and peptides as well as their naturally occurFrom the ‡Dipartimento di Scienze Applicate ai Biosistemi, Università di Cagliari,

No abstract

Proteomic platforms can be classified in bottom-up strategies, which analyze the sample after proteolytic digestion, and top-down strategies, which analyze the intact naturally occurring proteome. Bottom-up platforms are high-throughput because they can investigate a large number of proteins, regardless of their dimension. Nonetheless, information on post-translational modifications (PTMs) can be lost, especially those regarding naturally occurring cleavages and alternative splicing. Top-down platforms cannot cover vast proteomes, however, they can disclose subtle structural variations occurring during protein maturation and allow label-free relative quantifications in an unlimited number of samples. A repertoire of 256 masses belonging to naturally occurring proteins and peptides consistently detected by RP-HPLC-ESI-MS analysis of the acidic soluble fraction of human whole saliva is presented in this study. Of them, 233 have been identified, while 23 are still pending for the definitive characterization. The present review reports average and mono-isotopic masses of the peptides and proteins detected, RP-HPLC elution times, PTMs, origin and quali-quantitative variations observed in several physiological and pathological conditions. The information reported can be a reference for users of top-down RP-HPLC-ESI-MS proteomic platforms applied to the study of the human salivary proteome as well as of other human bodily fluids.

Thymosin beta(4) (Tbeta(4)), its sulfoxide, and thymosin beta(10 )(Tbeta(10)) were detected in human saliva and identified by different strategies based on RP HPLC coupled to electrospray multidimensional IT MS. Tbeta(4 )was almost always detected in whole saliva, its sulfoxide sporadically, Tbeta(10) rarely. Tbeta(4) was undetectable in parotid saliva and less concentrated in submandibular/sublingual saliva than in whole saliva. Analysis of gingival crevicular fluid revealed high relative amounts of Tbeta(4), Tbeta(4) sulfoxide, and Tbeta(10) in all the samples. Tbeta(4) mean concentration was 200 times higher in crevicular fluid (20 micromol/L, N = 9) than in whole saliva (0.1 micromol/L, N = 9). Crevicular fluid concentration of Tbeta(4 )(ca. 5% represented by its sulfoxide) and beta(10 )significantly correlated (r = 0.856; N = 9), and their ratio was about 5. A significant correlation was also observed between Tbeta(4 )concentrations in whole saliva and gingival crevicular fluid (r = 0.738; N = 9). Immunohistochemical analysis of the major salivary glands showed that immunoreactivity for Tbeta(4) is restricted to ductal cells, with minor degree of focal positivity in some acinar cells. On the whole, results indicate that gingival sulcus is a main, although not the sole, source for oral Tbeta(4 )and Tbeta(10).

Lo studio della proteomica salivare, test economico e non invasivo, rappresenta una fonte di numerose informazioni, ed è utile per la diagnosi di svariate malattie. Da quando siamo entrati nell’era della tecnologia genomica e delle scienze “omiche”, la raccolta di campioni salivari è aumentata esponenzialmente. Recenti piattaforme proteomiche hanno analizzato il proteoma salivare umano, caratterizzando circa 3000 peptidi e proteine, espressi in maniera differente: più del 90% in peso deriva dalla secrezione delle tre ghiandole salivari maggiori, mentre la restante parte proviene dalle ghiandole salivari minori, dal fluido crevicolare gengivale, da essudati mucosi e dalla microflora orale. L’obiettivo principale dell’analisi proteomica è discriminare tra condizioni fisiologiche e patologiche. Ad oggi, tuttavia, non esiste un preciso protocollo che permetta di analizzare l’intero proteoma salivare, pertanto sono state realizzate svariate strategie. Innanzitutto, è possibile distinguere due tipologie di piattaforme proteomiche: l’approccio “top-down” prevede l’analisi delle proteine sotto esame come entità intatte; nell’approccio “bottom-up” la caratterizzazione della proteina avviene mediante lo studio dei peptidi ottenuti dopo digestione enzimatica (con tripsina tipicamente). A causa di questa eterogeneità, per una stessa patologia sono stati proposti differenti biomarkers. Il proteoma salivare è stato caratterizzato in numerose malattie: carcinoma squamoso e leucoplachie orali, malattia del trapianto contro l’ospite (GVHD) cronica, sindrome di Sjögren e altri disordini autoimmuni come la sindrome SAPHO (sinovite, acne, pustolosi, iperostosi e osteite), schizofrenia e disordine bipolare, malattie genetiche come la sindrome di Down o la malattia di Wilson. In conclusione, i risultati delle ricerche riportate in questa review suggeriscono che nel prossimo futuro la saliva diverrà un fluido di indubbia rilevanza diagnostica utile per fini clinici, sia diagnostici, sia prognostici.