Proteomic (HLPC-ESI-MS) study of salivary peptides and proteins in patients with Sjögren's syndrome. before and after pilocarpine

Saliva is a complex fluid composed of a variety of electrolytes, metabolites, nucleotides, polynucleotides and proteins; it plays an important role in the maintenance of oral health (1). The rate of salivary protein secretion is controlled mainly by noradrenalin that is released from the sympathetic terminals and acts through the β-adrenergic receptors, while the rate of fluid and electrolyte secretion is controlled by acetylcholine, released from the parasympathetic terminals and acting through the muscarinic cholinergic receptors (2). A large number of systemic agents has been proposed as secretagogues, but only a few have shown consistent salivary secretion enhancing properties in well-designed trials. Among cholinergic agonists, pilocarpine is the most effective for protein secretion in rat (3), having also a mild β-adrenergic stimulating properties, but a few data have been reported in humans. Pilocarpine has been shown to improve symptoms of oral dryness and to increase salivary output in patients with primary Sjögren’s syndrome (pSS) (4), a chronic autoimmune disorder of the exocrine glands with associated lymphocytic infiltrates and consequent dryness of mouth and eyes (5). Saliva composition in pSS patients has been found to be different from normal subjects (6). However the pattern of salivary gland proteins in patients with pSS is not completely defined with regard to its composition, mainly in relation to low-molecular-weight components as acidic and basic proline-rich proteins (PRPs), statherins and cystatins, as well as defensins, which are immunopeptides of epithelial and neutrophilic origin, and thymosins, G-actinsequestering peptides with immuno-regulatory properties. In particular there are no data concerning the effects of pilocarpine on salivary protein profile in pSS patients. Moreover there are no studies on the possible differences in salivary protein profile between pSS and Sjögren’s syndrome associated to other rheumatic diseases (sSS).